Editing 2867: DateTime
Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.
The edit can be undone.
Please check the comparison below to verify that this is what you want to do, and then save the changes below to finish undoing the edit.
| Latest revision | Your text | ||
| Line 13: | Line 13: | ||
[[Ponytail]] asks [[Cueball]] how to calculate the time elapsed between two instants. A Cueball not intimately familiar with the complexities of the way humans measure time naively assumes that this is given by the difference of the timestamps. A Cueball who is familiar panics and states that it is impossible to know, and further that it is forbidden to even ask the question. | [[Ponytail]] asks [[Cueball]] how to calculate the time elapsed between two instants. A Cueball not intimately familiar with the complexities of the way humans measure time naively assumes that this is given by the difference of the timestamps. A Cueball who is familiar panics and states that it is impossible to know, and further that it is forbidden to even ask the question. | ||
| − | Randall's use of the term "DateTime systems" covers [https://metacpan.org/pod/DateTime any] [https://docs.python.org/3/library/datetime.html number] [https://learn.microsoft.com/en-us/dotnet/api/system.datetime?view=net-8.0 of] [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date situations], and the complexities are hardly confined to any particular programming language, or indeed computers as a whole. Some of these complexities include time zones (and changes to time zones), the international date line, daylight saving time and differing observation (or non-observation) thereof in different areas (and changes to the observation of daylight saving time over time), leap days and leap seconds, etc. Another complexity is found in relativistic effects, in which the flow of time varies depending on how deep in a gravity well one is; {{w|Barycentric Coordinate Time}} and {{w|Geocentric Coordinate Time}} (in French, TCB and TCG respectively - the reference to TGC in the title text appears to be a typo) are time systems used for space missions and orbit calculations that handle this | + | Randall's use of the term "DateTime systems" covers [https://metacpan.org/pod/DateTime any] [https://docs.python.org/3/library/datetime.html number] [https://learn.microsoft.com/en-us/dotnet/api/system.datetime?view=net-8.0 of] [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date situations], and the complexities are hardly confined to any particular programming language, or indeed computers as a whole. Some of these complexities include time zones (and changes to time zones), the international date line, daylight saving time and differing observation (or non-observation) thereof in different areas (and changes to the observation of daylight saving time over time), leap days and leap seconds, etc. Another complexity is found in relativistic effects, in which the flow of time varies depending on how deep in a gravity well one is; {{w|Barycentric Coordinate Time}} and {{w|Geocentric Coordinate Time}} (in French, TCB and TCG respectively - the reference to TGC in the title text appears to be a typo) are time systems used for space missions and orbit calculations that handle this. A partial list of such minutiae may be found at [https://gist.github.com/timvisee/fcda9bbdff88d45cc9061606b4b923ca Falsehoods Programmers Believe About Time]. The title text of the comic also references some of them. Depending on when T1 and T2 are, changes in calendar system may also be a relevant consideration—perhaps most famously, the change from the Julian calendar and the Gregorian calendar, two calendar systems which are nearly identical but nearly two weeks apart, and which different countries changed at different times. |
The statement that "it is impossible to know" is because Ponytail did not provide enough information in the question: She needed to specify the location and time zone of both observations, and possibly the exact values of T1 and T2 to the nanosecond. Considering the restrictions imposed by relativity on two observers agreeing on the timing of events, it may be literally impossible to determine a value of T2 - T1 that is absolutely "correct" to arbitrary levels of precision. | The statement that "it is impossible to know" is because Ponytail did not provide enough information in the question: She needed to specify the location and time zone of both observations, and possibly the exact values of T1 and T2 to the nanosecond. Considering the restrictions imposed by relativity on two observers agreeing on the timing of events, it may be literally impossible to determine a value of T2 - T1 that is absolutely "correct" to arbitrary levels of precision. | ||
