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How to ensure monotonic nondecreasing timeHow to ensure monotonic nondecreasing timePosted Nov 17, 2006 23:09 UTC (Fri) by giraffedata (subscriber, #1954)In reply to: How to ensure monotonic nondecreasing time by zooko Parent article: Counting on the time stamp counter
Programmers need to realize that they cannot have both monotonically non-decreasing (or monotonically increasing) *and* "correlates to shared human date-time e.g. UTC". Can you elaborate? I think you're saying that if I want a clock that correlates to UTC, it must necessarily step backwards sometimes. I don't see why.
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How to ensure monotonic nondecreasing time Posted Nov 29, 2006 12:37 UTC (Wed) by robbe (guest, #16131) [Link] I guess zooko allured to leap seconds, where UTC stands still for(acually: jumps backwards by) a second. Maybe keeping TAI and the current delta is the answer to this one?
How to ensure monotonic nondecreasing time Posted Nov 29, 2006 17:19 UTC (Wed) by giraffedata (subscriber, #1954) [Link] I guess zooko alluded to leap seconds, where UTC stands still for (actually: jumps backwards by) a second. Ah. That's probably it. Except that UTC does not stand still or go backwards. When there's a leap second, UTC goes steadily forward from 23:59:59 to 23:59:60 and then to 00:00:00. Note that a UTC time of day is a tuple of numbers (year, month, day, hour, minute, second). But the standard Linux time representation (a single number) does step backward at leap second time; it's defined that way to make it easy to compute UTC from it. And I think zooko's statement that a programmer can't have a time that is both monotonically nondecreasing and correlates to a human time standard has to be qualified to the case that the time is represented by a single number. As long as you're willing to work with multiple numbers, two obvious ways are TAI + delta as you suggest, and just plain UTC.
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