I think your issue title might be confused (backwards)?

Yes. I hope the document will contain more information around the topics I mentioned, to correct me.

Incremental time is just a number of clock ticks since an arbitrary epoch. Any field computation on an incremental time depends on a calendar and at least an LTO (defaulting to UTC, or, ideally, a timezone instead of an LTO).

I'm guessing LTO means something like local time offset?

Incremental times, thus, have nothing to do with DST or leap years or even leap seconds, since it is the calendar and/or time zone that deals with these concepts when converting the monotonic time into date/time field values.

Leap seconds are a special topic. In general, many systems and specifications (HTML is one such) ignore leap seconds and work in a proleptic manner (usually the error builds up the further back in time you look). This is bad for certain applications, but for most applications, since there are only 27 total leap seconds and since hardware clocks are often not that accurate, it's not specifically important. Millisecond accuracy is not usually expected for events in 1972 CE.

As you note, system time can "jump around" because of changes to the system clock. Most applications do not notice non-contiguous non-monotonic time because they are not watching the clock's value, only querying it sporadically (they also assume that the close was set correctly at some point--not always a good assumption!). Large jumps can occur, such as when the system's internet connection is down.

I kind of mixed up the discrete timelines (e.g. ghost times due to DST) with the APIs. I believe the below should be a correct representation of... time?

TAI (International Atomic Time): Pure count of SI seconds. The canonical timeline lives here. Only here can there be no ghost times.
UTC: Synchronized to mean solar time (Is mean solar time observed time?) by adding leap seconds. Note that leap seconds can't be computed/predicted into the future.
Civil calendar (e.g. the Gregorian calendar): Leap days are only defined by the calendar, and handled by e.g. UTC as regular days. In other words, leap days are inserted into the calendar when mapping a day count (UTC) to years, months and days. The Gregorian calendar's leap year rules can be computed into the future (specified that UTC is used).
Time zones: Offsets times forward and backward usually up to 12 hours. When in time zone definitions don't change, they don't add ghost times.
DST: Jumps clocks forward and backward seasonally. Can be thought of like time zones that change definitions twice a year.

I think your notes are interesting and useful to the discussion in the document and I'll look for a way to incorporate them.

Thank you!

Uh oh!

Mention that incremental time does not count leap seconds, leap years or DST #27

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