11.3. Datetime Standards

  • Date and time formats varies from country to country 19

11.3.1. Date

Formal date format in USA 26:

4/12/61
April 12, 1961

Formal date format in Japan 25:

61/04/12
1961年04月12日

20/12/31
平成20年12月31日

Formal date format in Germany:

12.04.1961

Date format in Poland:

12 kwietnia 1961
12 kwiecień 1961

12 IV 1961
12.IV.1961

12.4.1961
12.04.1961

12/4/1961
12/04/1961

12-04-1961
1961-04-12

Which format is a formal standard in Poland? 24

11.3.2. Time

  • What AM stands for?

  • What PM stands for?

  • 24 and 12 hour clock

  • Zero padded minutes, seconds and microseconds but not hours

  • Variable length microseconds

  • Confusion at noon and midnight

24 and 12 hour clock:

5:00 AM
5:00 PM
5:00
17:00

Zero padded:

06:07
6:07

06:07:00
6:07:00

6:07:00.000001
6:07:00.123456
6:07:00.123
6:07:00.1

Noon and Midnight

  • Which time is a midnight?

  • Which time is a noon?

  • Confusion at noon and midnight 20

  • Is 12:00 a noon (in 24h format), or someone just simply forgot to put AM/PM?

12:00 am
12:00 pm

12:00
24:00

00:00
0:00

11.3.3. Times after 24:00

  • Times after 24:00 21

  • UTC leap second 18

  • Leap second discontinuation post 2035 1

  • Issues created by insertion (or removal) of leap seconds

  • Calculation of time differences and sequence of events

  • Missing leap seconds announcement

  • Implementation differences

  • Textual representation of the leap second

  • Binary representation of the leap second

  • Other reported software problems associated with the leap second

23:59:59
23:59:60

25:00
27:45

14:00-30:00

11.3.4. Decimal Time

  • Unix time gives date and time as the number of seconds since January 1, 1970

  • Microsoft's FILETIME as multiples of 100ns since January 1, 1601

  • VAX/VMS uses the number of 100ns since November 17, 1858

  • RISC OS the number of centiseconds since January 1, 1900

Source: 17

11.3.5. Other

  • Military time 22

  • Military time zones 23

  • Swatch Internet Time - Beats @300 7

  • sidereal day on Earth is approximately 86164.0905 seconds (23 h 56 min 4.0905 s or 23.9344696 h)

11.3.6. Calendars

  • Julian Calendar 8

  • Gregorian Calendar 3

  • List of adoption dates of the Gregorian calendar by country 2

  • There are only four countries which have not adopted the Gregorian calendar: Ethiopia (Ethiopian calendar), Nepal (Vikram Samvat and Nepal Sambat), Iran and Afghanistan (Solar Hijri calendar)

11.3.7. Astronomy

  • Synodic day - the period for a celestial object to rotate once in relation to the star it is orbiting 10

  • Solar time - calculation of the passage of time based on the position of the Sun in the sky 9

  • Epoch (astronomy) 5

  • Sidereal Time 4

  • JD - Julian Day 6

11.3.8. Space Industry

  • UTC - Coordinated Universal Time 13

  • GMT - Greenwich Mean Time 11

  • MET - Mission Elapsed Time

  • Relativistic effects

  • Time dilatation due to speed approaching speed of light

11.3.9. Planet Mars

  • MSD - Mars Sol Date 15

  • MTC - Coordinated Mars Time 16

  • Timekeeping on Mars 14

  • Mars Clock 12

  • Martian sidereal day is 24 h 37 m 22.663 s (88,642.663 seconds)

  • Martian solar day is 24 h 39 m 35.244 s (88,775.244 seconds)

11.3.10. References

1

Gibney, E. The leap second's time is up: world votes to stop pausing clocks. Year: 2022. Retrieved: 2022-11-18. URL: https://www.nature.com/articles/d41586-022-03783-5 DOI: https://doi.org/10.1038/d41586-022-03783-5

2

Wikipedia. List of adoption dates of the Gregorian calendar by country. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/List_of_adoption_dates_of_the_Gregorian_calendar_by_country

3

Wikipedia. Gregorian Calendar. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Gregorian_calendar

4

Wikipedia. Sidereal Time. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Sidereal_time

5

Wikipedia. Epoch Astronomy. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Epoch_(astronomy)

6

Wikipedia. Julian Day. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Julian_day

7

Wikipedia. Swatch Internet Time. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Swatch_Internet_Time

8

Wikipedia. Julian Calendar. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Julian_calendar

9

Wikipedia. Solar Time. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Solar_time

10

Wikipedia. Synodic Day. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Synodic_day

11

Wikipedia. Greenwich Mean Time. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Greenwich_Mean_Time

12

Wikipedia. Mars Clock. Year: 2022. Retrieved: 2022-05-10. URL: https://marsclock.com/

13

Wikipedia. Coordinated Universal Time. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Coordinated_Universal_Time

14

Wikipedia. Timekeeping On Mars. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Timekeeping_on_Mars

15

Wikipedia. Timekeeping On Mars - Mars Sol Date. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Timekeeping_on_Mars#Mars_Sol_Date

16

Wikipedia. Timekeeping On Mars - Coordinated Mars Time. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Timekeeping_on_Mars#Coordinated_Mars_Time

17

Wikipedia. Metric time. Leap Second. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Metric_time

18

Wikipedia. Leap Second. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Leap_second

19

Wikipedia. Date Time Formats. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/Date_format_by_country

20

Wikipedia. Noon Midnight. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/12-hour_clock#Confusion_at_noon_and_midnight

21

Wikipedia. Times After 2400. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/24-hour_clock#Times_after_24:00

22

Wikipedia. Military Time. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/24-hour_clock#Military_time

23

Wikipedia. Military Timezones. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/List_of_military_time_zones

24

Wikipedia. ISO8601. Year: 2022. Retrieved: 2022-05-10. URL: https://en.wikipedia.org/wiki/ISO_8601

25

Date and time notation in Japan. Wikipedia. Year: 2022. Retrieved: 2019-06-27. URL: https://en.wikipedia.org/wiki/Date_and_time_notation_in_Japan#Date

26

Date and time notation in the United States. Wikipedia. Year: 2022. Retrieved: 2019-06-27. URL: https://en.wikipedia.org/wiki/Date_and_time_notation_in_the_United_States