WO2009056800A1

WO2009056800A1 - Time zone calculator

Info

Publication number: WO2009056800A1
Application number: PCT/GB2008/003589
Authority: WO
Inventors: David Richard Wille
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-10-29
Filing date: 2008-10-23
Publication date: 2009-05-07
Anticipated expiration: 2010-04-29

Abstract

The invention relates to a time zone calculator for simultaneously comparing one or more times in a first time zone with the corresponding time in a second time zone, said calculator comprising first and second time scales (7, 9) each of which are marked with twenty four numbered divisions representing twenty four hours of the day, wherein said first and second time scales (7, 9) are independently moveable (3) and characterised in that both scales contain geographic information (6, 8) which corresponds to particular countries and/or cities (6, 8) within a plurality of time zones, such that one or more times in a country and/or city within a first time zone can be correlated with a corresponding time in a country and/or city within a second time zone.

Description

TIME ZONE CALCULATOR

The invention relates to a time zone calculator for simultaneously comparing a plurality of times in a first time zone with the corresponding time in a second time zone.

At any given instance, universal time is the same simultaneously at all global locations. Many regional or national administrations, however, use local conventions for reporting time for which this is no longer true. At different global locations, commonly for this purpose labelled as and ordered into time zones, the same universal times may be reported differently as differing local times and any differences in local time at these locations must be taken into account when citing or comparing times between them. With the ever increasing rise in international travel and high speed communications, such considerations are of frequent practical relevance. Not only is it generally useful to be able to compute the extent of time differences between different locations or time zones, but methods are often required to compare local times between different global locations, possibly further adjusted to maximise the number of usable daylight hours (daylight saving time), in order to establish a common agreement in describing common time between them. Example requirements include not only the discussion of single instances, such as the time of an aircraft's arrival or the start of a telephone conversation, but also the comparison of entire time periods, or intervals, between time zones. Examples of this second type of task include finding the best times for meetings across time zones or the planning of other joint or personal activities. When resolving such issues it is often important that any considerations or comparisons of local time differences should be easy and effective to enact without extensive reference or calculation. This is a requirement which is not easy to achieve.

To address such problems, a number of practical devices have been proposed which each provide methods for a partial solution of these needs but each of which are unable to address them all simultaneously. Such limitations result in a corresponding restriction on the devices' practical applicability. Two such inventions based upon the use of rotating disks and scales are cited below and are described by the patents US1607560 and GB1407597 to illustrate the relevant features of these devices.

The device described in US1607560 uses a system of two rotating scales - a time zone scale and a 24 hour time scale - to display, for any given selected time, the local times at all global locations at that selected time simultaneously. Although this is of undoubted value for the calculation of time zone differences, and the explanation of their derivation, it is of less practical use where multiple times are to be computed (e.g. a time interval) between just two geographic locations. For each new time, the disks must be readjusted, and for different ranges of times, such as when for example to try to find and arrange a commonly available time for a cross time zone meeting, several realignments may be necessary. For such common practical applications, or say for example where the user is interested in merely exploring the implications of a time difference across their working day, this places a major restriction on the practical ease of use of this device.

The device described in patent number GB1407597 by contrast uses two rotating 24 hour time scales to allow for simultaneous comparisons of multiple times and time intervals which addresses the issues cited above for patent US1607560. Although this has clear practical advantages where time intervals are to be compared, the device lacks a system for computing the relative time difference between pairs of time zones and requires this to be provided separately by the user in advance before the device can be used. Since these time differences are in general not known, but require separate calculation or reference, this represents a severe practical limitation on the use of this device. According to a first aspect of the invention, there is provided a time zone calculator for simultaneously comparing one or more times in a first time zone with the corresponding time in a second time zone, said calculator comprising first and second time scales each of which are marked with twenty four numbered divisions representing twenty four hours of the day, wherein said first and second time scales are independently moveable and characterised in that both scales contain geographic information which corresponds to particular time zone names or locations within a plurality of time zones, such that one or more times in a location within a first time zone can be correlated with a corresponding time in a location within a second time zone.

The invention proposes an alternative method for the calculation of local times between global locations using a rotational system of two geographic and two 24 hour scales, both contained within the above first and second time scales, which overcomes the problems of previously known devices. These are constructed so as not only to be able to calculate the difference in local time between two pairs of locations but also to be able to, at a glance and without readjustment of the scales, allow the comparison of all the corresponding equivalent local times throughout the daily 24 hour cycle. The invention thus addresses a commonly arising practical need by allowing a user to quickly and easily determine, for any pair of geographic locations, not only an abstract time difference or the local time at a single specific instance in time but also its practical implications for arranging one's working day or other concrete activities across a 24 hour period. In particular, this is allowed without multiple calculations or separate devices or references.

The equivalent local times corresponding to any time difference, or pair of time zones or locations selected for comparison by the alignment of the two geographical scales above, can be read and easily compared by reviewing the resulting relative alignment of a further pair of scales showing the hours or time points in the 24 hour day. Once aligned for any time difference or pair of selected geographic locations or time zones, all local times in the 24 hour day can thus be compared between the two time zones or locations without need for any re-adjustment, movement or further realignment of the device's scales.

In one embodiment, the location comprises the name of a country and/or a city.

In one embodiment, the twenty four numbered divisions comprise twenty four hour numbering from 1 to 24 or 0 to 23. In an alternative embodiment, the twenty four numbered divisions comprise twelve hour numbering from 12am to 11am and 12pm to 11pm.

In one embodiment, said geographic information comprises the name of said country and/or city or a specific time zone region. Examples of suitable time zone regions include Eastern Standard Time in the United States and Time Zone 22. In an alternative embodiment, said geographic information comprises a graphical image or atlas representation relating to said country and/or city.

In one embodiment, the first and second time scales are displayed on one or more disks, such as two or three disks which are rotatably moveable with respect to each other. In a further embodiment, the first and second time scales are displayed on first and second circular scales, such as disks, which are rotatably moveable with respect to each other. For example, the scales are printed on two separate disks (each containing a 24 hour time scale and geographic information) in such a way such that they can be rotated and aligned to determine time differences between different locations and the corresponding equivalent local times. Examples and illustrations of possible embodiments are shown in further detail below. Thus, the difference in local time between any two time zones can be easily calculated by the relative alignment of a pair of circular scales both bearing geographic indications and/or time zone designations.

In one embodiment, said disks are connected via a pin or pivot. In a further embodiment, the two disks are fastened to each other at the centres of their scales by a pin or pivot around which at least one is able to freely rotate.

In one embodiment, at least one of said disks comprises transparent material.

In one embodiment, the calculator additionally comprises a window portion for aligning two countries and/or cities within separate time zones.

For example, at least one of the disks is printed on a transparent material, or a material equipped with holes or windows, to allow for the easy adjustment and alignment of the scales printed on the two disks during the course of the device's operation.

In one embodiment, the device can be fitted with a suitable window, marker or pointer, possibly on an additional disk, which can be rotated or aligned to remind the user of the names or identities of the two time zones or geographic locations currently being compared.

In one embodiment, the calculator additionally comprises means to measure the relative time difference between the two selected time zones. In a further embodiment, the calculator additionally comprises indicating means to highlight the relative time difference between the two selected time zones, such as a pointer, marker or window. For example, the device can be equipped with a pointer or marker to display and, if necessary, modify the absolute time difference between the selected geographic locations or time zones. In one embodiment, the calculator additionally comprises means to measure the relative time difference between two different times. In a further embodiment, the measurement means comprise a scale printed on an additional disk (which may optionally be a detachable disk).

In one embodiment, the calculator additionally comprises retention means configured to restrict movement of the first and second time scales once two differing time zones have been selected. In a further embodiment, said retention means comprise a series of co-operating holes and studs or a retaining clip. In this embodiment, the device is fitted with a collection of holes and one or more studs, or an additional or alternative system using a clip or other physical restraint, to restrict and/or lock the rotation of the disks once a pair of time zones has been selected and their alignment is being used to compare local times between their two locations.

In one embodiment, the device optionally can be constructed or designed in such a manner as to allow additional space on one or more of its disks suitable for carrying advertising or corporate slogans, or other information, which may be of additional interest or use to the user.

In one embodiment, the calculator additionally comprises means to account for daylight saving time. It will be appreciated that certain embodiments of the invention contain two disks each of which contain a combined 24 hour time scale and geographic information scale. In the embodiment which comprises means to account for daylight saving time, said means comprise at least two symbols on each of a 24 hour time scale and a geographic information scale, obtained by separating one of said first and second time scales to correspond to the use or non-use of daylight saving time.

In one embodiment, at least one of said first and second time scales contains the twenty four numbered divisions and the geographic information on two separate daylight saving scales, wherein said means comprise symbols located upon each daylight saving scale configured such that alignment of said symbols results in adjustment between the twenty four numbered divisions and the geographic information by the appropriate daylight saving timeshift, such as one hour.

In one embodiment, the calculator comprises retention means configured to restrict movement between the two daylight saving scales once the daylight saving time has been adjusted. In a further embodiment, the retention means comprise a series of co-operating holes and studs or a retaining clip.

In this embodiment, the relative alignment between a time zone or location scale and a time scale can be optionally adjusted to account for possible differences in the local use of daylight saving between different locations. Therefore, provision is made for accommodating differences between standard time and daylight saving time at different locations as dictated by differences in customs or by regional or national administrations. Implemented by a system of two matching daylight savings scales, this is both easy to use and removes the need for alternate or replaceable scales as proposed by other devices, for example FR2606914B1 or EP0488114A1. An ability to easily adjust for daylight differences is of frequent practical value since the use or non-use of daylight time differs considerably between different geographic or political administrations. Many administrations, commonly for example in Asia, currently no-longer use daylight saving time at all. Further more, even if daylight saving time is used, its use may start and end on different dates or times of the year, as for example between locations in the Northern and Southern hemispheres.

In one embodiment, the device is extended so that the relative orientation of a time zone or location scale and a 24 hour time scale can be used to take into account local differences in the use of daylight saving time. The effects of said differences can be determined by the alignment of a pair of further scales carrying symbols corresponding to different conventions in the use of daylight saving time.

In one embodiment, to accommodate possible differences in the use of daylight saving time, the scales are printed on three separate disks in such a way that the scales can be rotated and aligned to compare local and daylight saving times between different locations.

In one embodiment, three disks described above are fastened to each other at their centres so they are able to freely rotate with respect to each other.

In one embodiment, the middle and upper disks are both printed on transparent material, or a material equipped with holes or windows, to allow for the easy adjustment and reading of scales printed on the three disks during the device's operation.

In one embodiment, the device can also be optionally fitted with a further collection of holes and studs, or a modification of the previous system for two disks, or an additional or alternative system using a clip or other physical restraint, to restrict and/or lock the rotation of the disks carrying the two daylight saving scales once the device is in operation.

In one embodiment, the device may be fitted with and additional disk, placed above the other disks and able to rotate freely around their common centre, equipped with a scale to measure the duration of any interval or period aligned on the 24 hour time scales.

It will be appreciated that although the time zone calculator of the invention may be constructed from a series of disks it is also envisaged that the calculator may be provided as a machine readable medium. Thus according to a further aspect of the invention, there is provided a machine readable medium containing instructions which when read by said machine provide the time zone calculator of the invention.

In one embodiment, the machine readable medium comprises any of the following: a floppy disk, a CD ROM, a DVD ROM / RAM (including a -R/-RW and + R/+RW), a hard drive, a memory (including a USB memory key, an SD card, a Memorystick™, a compact flash card, or the like), a tape, any other form of magneto optical storage, a transmitted signal (including an Internet download, an FTP transfer, etc), a wire, or any other suitable medium.

It will also be appreciated that the time zone calculator may comprise an electronic device or processing means. Thus according to a further aspect of the invention there is provided a machine arranged to provide the time zone calculator of the invention. In one embodiment, the machine is a personal computer, laptop, PDA, mobile telephone or satellite navigation device.

According to a further aspect of the invention, there is provided a method of simultaneously comparing one or more times in a first time zone with the corresponding time in a second time zone, said method comprising the step of aligning first and second time scales of a time zone calculator as defined hereinbefore.

According to a further aspect of the invention, there is provided a method of simultaneously comparing one or more times in a first time zone with the corresponding time in a second time zone while taking account of daylight saving time, said method comprising the step of aligning the symbols on each of said daylight saving scales of a time zone calculator as defined hereinbefore. According to a further aspect of the invention there is provided a method including a system of rotating scales to compute local time differences between different time zones and to compare the local times between time zones

In one embodiment, the difference in local time between two time zones is calculated by the relative adjustment and alignment of two circular scales of time zone names, geographic locations or symbols.

In one embodiment, the results of a time zone calculation are displayed through the resulting relative orientation of a pair of rotating scales showing the hours or times of a 24 hour day.

In one embodiment, the calculation of the time differences between a given pair of time zones or geographic locations and the resulting comparison of multiple local times between the given time zones can be made without readjustment of the rotating scales.

In one embodiment, the computation of differences in local times between different time zones can be adjusted according to differences in the use of standard or daylight saving time at different times or locations.

In one embodiment, differences in the use of daylight saving times between any two locations can be adjusted for by the relative adjustment and realignment of the orientation between a time zone or geographic location scale and a scale showing hours or times in a 24 hour day.

In one embodiment, the relative orientation of a time zone or geographic location scale and a scale showing the hours or times of a 24 hour day is adjusted by the relative alignment of a pair of scales each containing at least two symbols corresponding to the use or non-use of daylight saving time. In one embodiment, the determination of the time difference between two time zones and the comparison between local time in those time zones can be effected by the rotation and alignment of a system of circular scales printed on two mechanical disks.

In one embodiment, the two disks are fastened to each other at the centres of their scales by a pin or pivot around which at least one is able to freely rotate.

In one embodiment, at least one of the disks is printed on transparent material, or equipped with holes or windows, to allow for the easily adjustment and alignment of the scales between the disks when the device is in operation.

In one embodiment, an optional additional disk is fastened to the other two disks by means of a common pivot which can be rotated or aligned to remind the user of the names or identities of the time zones or geographic locations being currently compared.

In one embodiment, an additional disk is optionally provided along with a pointer or marker to display and if necessary modify the absolute time difference represented between by the relative alignment of the two disks or sets of scales.

In one embodiment, the calculator is optionally equipped with a collection of holes and one or more studs, or an additional or alternative system using a clip or other physical restraint, to restrict the motion of the disks once a pair of time zones or geographical locations has been selected and the invention is being used to compare local times between these locations.

In one embodiment, the determination of the time difference between two time zones, the comparison between local time in those time zones and the possible effect of differences in the use or non-use of daylight saving time at locations within those time zones can be effected by the rotation and alignment of a system of circular scales printed on three mechanical disks.

In one embodiment, three disks are fastened to each other at the centres of their scales by a pin or pivot around which at least two are able to freely rotate.

In one embodiment, two of the disks are printed on transparent material, or equipped with holes or windows, to allow for the easily adjustment and alignment of the scales between the disks when the device is in operation.

In one embodiment, an additional disk is optional provided, able to rotate freely around a common pivot with the other disks and equipped with a scale to measure the duration of time intervals on one or both of the 24 hour time scales.

The invention will now be described by examples as illustrated by the following figures. Figures 1 to 7 illustrate a basic example of the invention whilst figures 8 to 25 describe a number of alternative versions or extensions. Specifically, figures 15-25 describe a modification to take into account differences in daylight saving time use between different locations. More specifically, these figures show figure 1 : a front view of the device, figure 2: a side view of the device, figure 3: a front view detail of the two disks before assembly, figure 4: a detail of the front of the lower disk, figure 5: a detail of the front of the upper disk, figure 6: a view of the device in use showing a time difference of zero, figure 7: a view of the device in use to compare times in London and New

York, figure 8: an alternative arrangement of time zone and 24 hour scales, figure 9: a further alternative arrangement of time zone and 24 hour scales, figure 10: a version of the invention using non-transparent disks, figure 11 : a version of the invention using two equally sized time zone scales, figure 12: a rear view prior to assembly of a version of the device with time zone scales printed on the rear, figure 13: a rear view of a version of the device with time zone scales printed on the rear when in use, figure 14: a version of the device with a stud and holes to immobilise the disks when it is use, figure 15: a front view of a version of the device showing the comparison between standard local time in London and daylight saving time in

Sydney, figure 16: a side view of an extended version of the device to accommodate differences in the use of daylight saving time between locations, figure 17: a front view of the lower disk of the version shown in figure 16, figure 18: a front view of the middle-disk of the version shown in figure 16, figure 19: a front view of the upper disk of the version shown in figure 16, figure 20: a front view of the version shown in figure 16 after assembly, figure 21 : an illustration of a comparison of local times in London and Sydney without adjustment for daylight saving time, figure 22: an illustration of a comparison of local times in London and Sydney where daylight saving time is taken into account, figure 23: a side view of an extension to the version shown in figure 16 showing studs and holes to restricted unwanted rotation between disks figure 24: a rear view showing an optional extension to restrict relative rotation of the lower two disks and figure 25: a front view of a version of the device with an additional disk to display durations of time intervals. ll examples, from the terms "front" and "above" will be used interchangeably ill the terms "from behind", "below" and "rear". The figures shown and the examples discussed are only representative of a selection of possible versions of the invention. Other versions are equally possible by changing the position, printing, orientation and ordering of the scales and/or the ordering of the disks.

Figure 1 shows one example of this invention viewed from the above. Two circular disks 1 and 2 are attached together at their common centres by a pin 3 or other suitable pivot about which at least one is allowed to freely rotate. The two disks 1 and 2 are made from rigid acetate, plastic or other rigid sheet or material on to which legends or symbols can be printed. The lower disk 2 can be opaque but the upper disk 1 is transparent. The lower disk 2 may be the same size as the upper disk 1 or, as in this figure, slightly larger consistent with the symbols and scales described by the following figures.

Figure 2 shows a side view of the construction with its upper side facing up showing again the upper and lower disks 1 and 2 and the central pivot or pin 3 about which they can turn passing through holes 4 and 5 at the centre of each disk.

Figure 3 shows a view of the device from the front prior to assembly with the transparent upper disk 1 on top and the lower disk 2 partly uncovered. 4 and 5 are the central holes through which the joining pin or pivot will be passed.

Figure 4 shows a detail of the lower disk viewed from above prior to assembly showing two printed scales 6 and 7 and the central hole through which the pivot is placed 5. The inner most scale 6 lists a sequence of time zone names, for each time zone, or example geographical locations. These are listed clockwise in order of increasing latitude east of the Greenwich meridian 0⁰E such that an angle of 15° corresponds to a local time difference of one hour. The outermost scale 7 lists the hours of a 24 hour day in ascending clockwise order at intervals of 15°. This is done by the numbers 01 for 01 :00 to 24 for 24:00. Thus, an increase of one hour on this scale 7 also corresponds of a clockwise angle of 15°. As shown in this figure, the two scales 6 and 7 are aligned so that the symbol for midnight (24 on the twenty-four hour time scale 7) is aligned with the label for a given time zone, here - for illustration - the time zone containing the Greenwich meridian 0⁰E labelled 'London'. Both scales share a common radius with centre at the centre 5 of the disk.

Figure 5 shows the corresponding front view of the upper disk. The two scales 8 and 9 are constructed in an identical manner to the scales 6 and 7 in figure 4 on the lower disk but are printed on circles of a slightly smaller radius so that when the upper disk is attached to the lower disk, they appear inside the corresponding lower disk's scales. As shown in this figure, the printing of the time zone names 8 on this upper disk is now right justified to aid comparison with the corresponding time zone scale on the lower disk. In this example of the invention, the scale on the lower disk can be viewed through the upper disk when the device is assembled since the upper disk is made of a transparent material. 4 shows the hole for the pivot by which the upper disk is attached to the lower disk.

Figure 6 gives a detail of the front view of these two scales once the two disks have been attached by means of the pivot 3 and completely aligned. 9 and 8 indicate the 24 hour and time zone scales respectively on the upper disk whereas 7 and 6 show the corresponding scales on the lower disk, scale 6 being visible through the upper disk. Since the manner of construction of these scales is identical, radially aligning two scales of the same type (e.g. the time zone labels) automatically aligns the other two (e.g. 24 hour times). This is illustrated in figure 6 by the identical times on the two time scales 9 and 7 aligned one inside each other given the agreement between time zones scales.

Figure 7 shows an example of how the invention can be used to compute time differences and convert local times between different time zones. In particular, it shows an illustration of the difference between local times in between London and New York. The figure is identical to figure 6 except that the disks have now been rotated relative to each other so that the symbol for London printed on the inner time zone scale 8 on the upper disk appears alongside the symbol for New York on the outer time zone scale 6 printed on the lower disk. The time difference between the local times in these two time zones is five hours, so this rotation corresponds to an angle of 5 x 15° = 75° relative to the position shown in figure 6. When so aligned, the two 24 hour time scales also differ by five hours and can be thus used to compare local times between London and New York, the two selected time zones. In particular, the values on the outer scale 7 correspond to the local time in New York whereas those on the inner scale 9 correspond to the local time in London. For example, the symbol 24 on the outer New York time scale 7 is now in line with 05 on the inner London scale 9 indicating that when it is midnight in New York, it is 05:00 in London. Other local times at these two locations can be compared in the same way without further rotating the disks, as can entire intervals. For example, a working day of 09:00 to 17:00 in London corresponds to 04:00 to 12:00 local time in New York.

Figure 1 described above also illustrates a use of the device, this time to calculate the time differences between London and Paris. With the outer time zone scale entry for London aligned with the inner time zone scale entry for Paris, local times for London are displayed on the outer 24 hour scale in London are aligned with the corresponding equivalent times for Paris on the inner 24 hour scale. As shown in this example, local time is one hour ahead in Paris of that displayed for London.

By matching the names of different time zones on the time zone scales printed on the upper and lower disks, any arbitrary pair of time zones can be compared and their relative local times computed. In particular, once the required time zones have been aligned, the corresponding local times are aligned one above each other on their respective inner and outer 24 hour time scales. For general use, examples of this invention could also include lists of alternative time zone names - or example geographic locations within time zones, or other references - printed on the device or on a separate reference. This could assist the user in quickly finding the appropriate time zone names or symbols to align the two disks. Further versions of the invention are illustrated by the following figures.

In figures 8 and 9, two alternative versions of the invention are shown from the front in which the layout of the scales has been changed and the time zones printed on a graduated scale 8 and 6 with the 24 hour scales 9 and 7 now on the inside of or, in figure 9, in between them. In either case, 9 and 8 are printed on the upper disk and 7 and 6 on the lower disk. Both disks are here the same size and the upper disk is again printed on transparent material such as acetate or rigid transparent plastic sheet. These devices, which are otherwise constructed in the same way as that described in figures 1 to 7 can be used in the same way by matching the symbols for the required time zones and comparing the times on the two 24 hour scales. By means of illustration, both figures - figure 8 and 9 - illustrate a comparison between the local times in London and New York.

Figures 8 and 9 also show the optional prevision for half hour time zones where the local time is an odd number of half hours ahead of or behind the Greenwich meridian (0⁰E, London). One example is Tehran (10 in figures 8 and 9) which is 3¹/4 hours ahead of London. In this example, half hourly time zones are printed midway between the adjacent hourly time zones and may be aligned with and compared to other time zones in exactly the same way as hourly time zones.

In figure 10, an example of the invention is presented printed entirely on opaque materials such as non-transparent plastic or paper card but otherwise identical to that described by figures 1 to 7. In this version, the time zone scale on the lower disk 2 is visible through the upper disk 1 by means of 24 windows 11 cut into the upper disk beside each entry on the upper disk's time zone scale. In figure 11 an alternative alignment of the two time zone scales is shown where they both are printed on circles of the same radius. To aid alignment, the time zone symbols or names are shifted half a line up for the upper disk (e.g. Moscow, 21) and half a line down for the lower disk (e.g. Beijing, 22). Time zones are then selected when the required symbols appear directly above and below each other. In figure 11 , Moscow, 21 , on the upper disk 1 and corresponding to the inner upper disk 24 hour scale is aligned with Beijing, 22, on the lower disk 2 which corresponds to the outer lower disk 24 hour scale. This implies, for example, that 16:00 in Moscow corresponds to 21 :00 in Beijing.

In this and other examples of the invention different colour, styles, or printing fonts can be used to visually associate matching time zones and 24 hour time scales. For example, all scales on the lower disk could be printed in red whilst those on the upper disk could be printed in black and bold.

In addition to the upper and lower disks 1 and 2, figure 11 also shows the addition of a further smaller disk 13 of a transparent, opaque or semi opaque material (e.g. plastic sheet or paper card) placed over and above the upper disk 1. This, which also rotates around the common central pivot 3, features a window 12, or visual cue, which can be rotated to place over and highlight the two selected time zones to remind the user, with the aid of the differing printing techniques described above, which time zone corresponds to which time scale.

Figures 12 and 13 show a rear view of an alternative version of the invention where the two time zone scales are alternatively or additionally printed on the rear of the device. An expanded view of the reverse of the two disks prior to assembly is shown in figure 12 whereas figure 13 shows a rear view of the version in use. The front of the device is equipped with two 24 hour time scales as shown in previous versions. The construction of this version is further described as follows. In figure 12, rear of the upper disk 1 is partly visible through a transparent window in the lower disk 2 which extends in from its boundary 16 to the central hole 5. This allows the time zone scale 14 on the rear of the lower disk 2 to be aligned with the corresponding time zone scale 15 on the rear of the upper disk 1 and so used to select the required relative orientation between the two disks needed to compare local times. Once aligned, local times for each of the two time zones can be compared using the two 24 hours scales printed on the front of the disks as in the above versions of this device. Note that to retain the same angular rotations between the two disks, the time zone scales in figures 12 and 13 are printed in reverse order, Paris, for example, is printed 15° anticlockwise from

London. Alternatively, if this order is not reversed, the device can still be used but the roles of the two 24 hour time scales printed on its front are exchanged. When assembled, the two disks are held together by a pivot though holes 4 and 5. Figure 13 illustrates this version in use where the lower disk time zone scale 14 is aligned with the upper disk scale 15 which is visible through the transparent window described for figure 12 above. In figure 13, London is aligned with New York thus allowing the comparison of the local time at these two locations on the two 24 hour scales printed on the front of the two disks.

Figure 12 also shows an optional additional scale 17 the reverse of the upper disk 1 indicating the number of hours by which each time zone lies behind a given reference location, here the Greenwich meridian (0⁰E). A window or mark 18 on the lower disk 2 placed in line with the reference location, here the Greenwich time zone, allows the hours difference in local time to be readily read for any alignment of selected time zones. An example view is shown through 18 in figure 13 where New York is 5 hours behind London and a time difference of -5 hours is shown. Since the device admits half hourly time zones, half hourly differences are also indicated on the scale. The angle between labels or symbols for consecutive differences is thus 7.5°. Figure 14 shows an expanded front view of a further version of this invention with 48 equally spaced holes 19 at 7.5° intervals on a transparent upper disk 1 on a circle with centre at the central pivot hole 4. With the aid of one or more studs 20 on the lower disk 2, these can be used to lock the device in a given alignment once the required time zones have been selected. This serves to stop the disks accidentally rotating when the invention is in use. In this version 48 holes at an interval of 7.5° are preferred to 24 at an interval of 15° to allow for half hourly rotations between the two disks. This is required for comparisons between hourly and half hourly time zones. In this example, the upper 1 and lower 2 disks are the same size.

An alternative version of this design fixes the rotational orientation of the two disks by a clip with an optional internal stud.

The following figures address comparisons between geographic locations with different daylight saving time regimes.

Daylight saving time is a convention used by some regional or national administrations where at certain times of the year, typically during the summer months, clocks are advanced by one hour ahead of standard time to increase the number of daylight hours in the afternoon or evening at the cost of reducing the number of daylight hours in the morning. Using the examples described above (figures 1 to 14), when comparing times between locations using daylight saving time with those without, the accommodation of such differences is also possible but requires an additional manual adjustment, or rotation, of the disks.

An example is shown in figure 15 where the comparative local times are obtained for the 1^st of January between London and Sydney, Australia. To correctly configure the two disks for use, the symbols for London and Sydney on the inner 9 and outer time zone 6 scales respectively are first aligned (not shown) without adjustment for daylight saving time as in previous examples of the invention. This gives an initial time difference of 14 hours between the two locations: a local time of 9:00 in London, for example, corresponds to an unadjusted local time of 19:00 in Sydney. If Sydney in January is on daylight saving (i.e. summer) time, however, and London is not, a one hour adjustment is needed to compare the effectively used local times at these two locations. In particular, since summer or daylight saving time is one hour ahead of standard time, 9:00 standard time in London now corresponds to 20:00 daylight saving time in Sydney. Rotating the outer Sydney time scale 7 by one hour, or 15°, clockwise relative to the inner London scale 9 brings 9:00 for London into alignment with 20:00 for Sydney as required. Moreover, once this is done, all other times throughout the 24 hour daily cycle are also correctly aligned and can so be compared using the two 24 hour time scales 7 and 8 as for previous versions. Specifically, local times on the outer time scale 7 for daylight saving times in Sydney now are now aligned with standard non-daylight saving times for London on the inner time scale 8. This is the final configuration shown in figure 15.

Figures 16 to 24 illustrate a further version of the invention using three disks to take into account possible differences between standard and daylight saving time by the addition of an extra disk and pair of scales.

Figure 16 shows a side view of this version where the three disks 21 , 22 and 23 are attached through their central holes by a central pivot or pin 24 around which at least two are allowed to freely rotate. The bottom disk 23 may be printed on transparent or opaque material whereas the upper two disks 22 and 21 are printed on rigid transparent sheet, or equipped with suitable viewing holes or windows. In this illustration, the lower 22 and middle 23 disks are the same size whereas the upper disk 21 is optionally smaller.

Figures 17 (the lower disk), 18 (middle disk) and 19 (upper disk) illustrate example scales printed on the top of each disk whilst figure 20 shows a top view of the version after assembly. In figure 20, 24 is the central pin or pivot. In this example of the invention, the construction of the scales on the top disk is the same as in the preceding two disk versions (see in particular scales 8 and 9 in figure 9) but the time and time zone scales on the original lower disk (e.g. scales 6 and 7 in figure 9) are now split between the lower and middle disks (23 and 22 in figure 16). In particular, the location or time zone scale 32 is printed on the lower disk (figure 17) and the corresponding 24 hour scale 30 is printed on the middle disk (figure 18). To align the lower 23 and middle 22 disks prior to use, a further pair of concentric scales 31 and 29 are provided both around their disk's central holes, and respective common centres, at 28 and 27 each with two symbols at a relative angle of 15° representing standard ("ST") and daylight saving ("DS") time. The different alignments needed to match the symbols on the two scales 31 and 29 can then be used to take into account differences in the use standard and daylight saving times between differing geographic locations. This is illustrated by figures 20 to 22.

Figure 20 shows a view of the example where all scales are fully in alignment. More precisely, by aligning the symbols on the two daylight saving scales 31 and 29 completely, so that DS is in line with DS and thus ST with ST, the relative alignment between the outer time zone or location scale 32 on the lower disk and the outer 24 hour scale 30 on the middle disk is the same as that printed on the lower disk of the two disk versions of this invention described previously (see figure 4 for an example). Providing that the thereby selected relative orientation between the lower and middle disks (23 and 22 in figure 16) is maintained, local times without any daylight saving adjustment can be compared as before by rotation of the upper most disk 21 , aligning the symbols on the outer and inner time zone scales 32 and 34 and reading off the resulting correspondingly aligned times from the 24 hour time scales 30 and 33.

An example of this is shown in figure 21 where the symbols corresponding to the two symbols for London and Sydney are first aligned respectively between the time zone scales 34 and 32 and the matching local times are then displayed on the corresponding 24 hour scales 33 and 30. As shown in figure 21, without adjustment for daylight saving time, 9:00 local time on the inner 24 hour scale 33 for London corresponds to 19:00 on the outer 24 hour scale 30 for Sydney, Australia.

Figure 22 shows an example of an alternative comparison where daylight saving is taken into account. In particular, times are again compared between London and Sydney but where Sydney is using daylight saving time whereas London is not. Specifically, the middle disk is rotated relative to the lower disk so that the symbol "DS" for daylight saving time on the outermost daylight saving scale 31 , printed with the outermost time zone scale 32 on the lower disk 23, is aligned with the symbol "ST" for standard time on the innermost scale 29 of the middle disk 22. This rotates the outermost 24 hour scale 30 by one hour, an angle of 15°, anticlockwise relative to the outermost time zone scale 33 causing the times on outer scale times for any given time zone location after the rotation to be one hour ahead of those (as shown in figure 21) prior to the rotation. This is sufficient to take into account the effect of daylight saving time. Keeping the lower two disks fixed, and rotating if necessary the top disk to align the respective symbols for London and Sydney on the inner and outer time zone scales 34 and 32 as before, now aligns standard non daylight saving times for London (inner 24 hour scale, 33) automatically against daylight saving times for Sydney (outer 24 hour scale 30) across the entire 24 hour daily cycle.

By rotating the two daylight savings scales 31 and 29 in this way, and aligning the symbols for standard or daylight saving time, any combination of daylight saving or standard local use between locations can be compared. Matching symbols on the inner daylight saving time scale 29 with those on the outer daylight saving scale 31 thus will cause the resulting times on the inner and outer 24 time hour scales 33 and 30 to be correctly aligned for any choice of geographic locations and choice of daylight saving regime. If the same daylight saving convention is used at both locations - either both are on standard time or both daylight saving - no adjustment is necessary and the both symbols, daylight saving and standard time, should be fully aligned. An example of this was illustrated in figure 21.

Before correcting for differences in daylight saving times, the user is required to know what local daylight saving policies are in force in the regional or geographic administrations between which time comparisons are required. Information relating to this may be printed on the device itself or supplied as accompanying documentation.

As for the two disk version illustrated in figure 14, this extended version can also be equipped with holes and one or more studs to restrict unwanted rotation between the disks when the device is in use. One possible two stud example is shown in figure 23 where two studs, 35 and 37, along with a system of holes, 36 and 38 are used to restrict unwanted rotation. Stud 35 and holes 36 restrict rotation between the two lower disks 23 and 22 once a combination of daylight saving settings has been selected whereas stud 37 and holes 38 restrict motion between middle 22 the upper disk 21 once two time zones or locations have been selected. As shown in the example illustrated by figure 14, to allow for all relative differences between possibly half hour time zones, 48 holes 38 are required on the upper disk. On the middle disk, however, only three holes 36 are required since only three relative rotations are needed between the lower 23 and middle 22 disks for different combinations of daylight saving time usage between locations.

Alternative or additional arrangements include one or more clips or other physical restraints, possibly also with studs, which can be applied or manipulated by the user to restrict and/or lock the motion of the disks as required.

Figure 24 shows an additional example of the device viewed from the lower or rear disk 23 where the lower and middle disks are fully aligned as in figures 20 and 21. To reduce unwanted relative rotations of the lower two disks (23 and 22 in figure 23) and the corresponding daylight saving scales (31 and 29 in figure 22), the middle disk (22 in figure 23) is provided with a stud (39 in figure 24) which passes through a matching arc shaped hole 40. This is so constructed to restrain the relative rotation of the two lower disks to ±15° from the fully aligned orientation shown in figures 20 and 21 and thus limits any rotation to the maximum range operationally required by the device. 24 is the central pivot as in previous figures.

Figure 25 shows an optional extension of this version where an additional disk 41 is added to measure length of time intervals simultaneously in each selected time zone. The new optional disk 41, made of transparent material, is placed above the existing three disks and allowed to rotate around the same common central pivot 24. It also carries an hourly scale 42, in this illustration calibrated in whole hours from 0 to 20. An example of its use is shown in figure 25 to compute departure and arrival times for a long haul summer flight between London and Beijing. After adjusting the daylight saving scales to take into account differences in the use of daylight saving time (here we assume that daylight saving time is in use in London, The United Kingdom, but not in Beijing, China), a departure time of 16:00 day light saving in London (inner scale) corresponds to 23:00 hours

(outer scale) standard time in Beijing. Rotating the zero on scale 42 on the upper most disk 41 to align with this time then indicates that after a 10 hour flight, the expected time of arrival in Beijing is 09:00 local time or 02:00 in London.

The examples and versions of the invention described above describe a practical tool which can be used to calculate differences in local times between different time zones. In particular, the use of a double time zone scale with two separate time zone scales allows for the easy one-step determination and exploration of the implications of time difference between different time zones not only at a single time but simultaneously between all possible times around the daily 24 hour cycle. This was not possible using any of the prior art cited above. Furthermore, this combined with the addition for a method for indicating the duration of a selected time interval and, more especially, a simple method for the accommodation of daylight saving differences, make this a practical device able to offer a solution many practical problems encountered whilst travelling, communicating or planning events across different time zones or local time conventions, and so address an unmet need.

Due to the simplicity of its construction, and the materials it uses, the invention is also suitable for mass production and distribution with minimum instruction and explanation. As such the device could also be distributed with advertising or other information, either accompanying it or printed on one or more of the disks, in order to attract attention to products or services, or to advertise a global image or operation.

Claims

1. A time zone calculator for simultaneously comparing one or more times in a first time zone with the corresponding time in a second time zone, said calculator comprising first and second time scales each of which are marked with twenty four numbered divisions representing twenty four hours of the day, wherein said first and second time scales are independently moveable and characterised in that both scales contain geographic information which corresponds to particular locations within a plurality of time zones, such that one or more times in a location within a first time zone can be correlated with a corresponding time in a location within a second time zone.

2. A calculator as defined in claim 1 wherein the twenty four numbered divisions comprise twenty four hour numbering from 1 to 24 or 0 to 23.

3. A calculator as defined in claim 1 wherein the twenty four numbered divisions comprise twelve hour numbering from 12am to 11am and 12pm to 11pm.

4. A calculator as defined in any preceding claims wherein said geographic information comprises the name of said country and/or city or a specific time zone region.

5. A calculator as defined in any of claims 1 to 3 wherein said geographic information comprises a graphical image or atlas representation relating to said country and/or city.

6. A calculator as defined in any preceding claims wherein the first and second time scales are displayed on one or more disks, such as two or three disks which are rotatably moveable with respect to each other.

7. A calculator as defined in claim 6 wherein said disks are connected via a pin or pivot.

8. A calculator as defined in claim 6 or claim 7 wherein at least one of said disks comprises transparent material.

9. A calculator as defined in any preceding claims which additionally comprises a window portion for aligning two countries and/or cities within separate time zones.

10. A calculator as defined in any preceding claims which additionally comprises means to measure the relative time difference between the two selected time zones.

11. A calculator as defined in claim 10 wherein the measurement means comprise a scale printed on at least one disk.

12. A calculator as defined in any of claims 10 or 11 which additionally comprises indicating means to highlight the relative time difference between the two selected time zones, such as a pointer, marker or window.

13. A calculator as defined in any preceding claims which additionally comprises means to measure the relative time difference between two different times.

14. A calculator as defined in claim 13 wherein the measurement means comprise a scale printed on an additional disk.

15. A calculator as defined in any preceding claims which comprises retention means configured to restrict movement of the first and second time scales once two differing time zones have been selected.

16. A calculator as defined in claim 15 wherein said retention means comprise a series of co-operating holes and studs or a retaining clip.

5 17. A calculator as defined in any preceding claims which additionally comprises means to account for daylight saving time.

18. A calculator as defined in claim 17 wherein at least one of said first and second time scales contains the twenty four numbered divisions and the

IO geographic information on two separate daylight saving scales, wherein said means comprise symbols located upon each daylight saving scale configured such that alignment of said symbols results in adjustment between the twenty four numbered divisions and the geographic information by the appropriate daylight saving timeshift, such as one hour.

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19. A calculator as defined in claim 18 which comprises retention means configured to restrict movement between the two daylight saving scales once the daylight saving time has been adjusted.

!0 20. A calculator as defined in claim 19 wherein said retention means comprise a series of co-operating holes and studs or a retaining clip.

21. A machine readable medium containing instructions which when read by said machine provide the time zone calculator as defined in any preceding claims.

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22. A machine arranged to provide the time zone calculator as defined in any of claims 1 to 20.

23. A machine as defined in claim 21 or claim 22 which is a personal 10 computer, laptop, PDA, mobile telephone or satellite navigation device.

24. A method of simultaneously comparing one or more times in a first time zone with the corresponding time in a second time zone, said method comprising the step of aligning first and second time scales of a time zone calculator as defined in any of claims 1 to 20.

25. A method of simultaneously comparing one or more times in a first time zone with the corresponding time in a second time zone while taking account of daylight saving time, said method comprising the step of aligning the symbols on each of said daylight saving scales of a time zone calculator as defined in any of claims 17 to 19.