[OskarS]

This is totally wrong, and a very dangerous way of handling date/time issues. If you set a wake-up alarm for 7am, you want that to go off at 7am in your local timezone, not 7am in whatever timezone you set the alarm in (which is what an ”absolute” time stamp would store).

There are lots of examples like this. Some time events you want to happen at absolute time points (in which case time zones are only for display purposes), but very often your events need to be ”time-zone aware”. There is no universal rule, and thinking that there is will lead to all sorts of trouble.

[lokedhs]

It's not wrong. What you're describing is not a timestamp.

A timestamp is a point in time, and is the same everywhere (excluding relativistic effects).

What you describe is definitely a valid use case (and having developed software that programs hardware that is controlled by a calendar, I have painful experience in this). However, it's not a timestamp. I'd call it time-of-day or wallclock. Some systems like SQL refers to it as simply "date" and "time". Whatever you prefer to call it, it's not a timestamp.

[Myrmornis]

Could you add something saying explicitly what a timestamp _is_ under your terminology? Is it an integer offset from the UNIX era start?

[lokedhs]

It's an abstract concept. It's nothing more than a given point in time.

How you represent it doesn't change the definition. It could be stored as the number of seconds since some arbitrary point in time, such as Unix timestamp, or a Julian timestamp.

Or, it could be a given time and date combination with some fixed point of reference, such as UTC. I'm sure we all have favourite ways of representing timestamps.

[Myrmornis]

Ok, one thing — perhaps not the most important — is that “timestamp” is a very unfortunate terminology for the abstract concept you describe. The word timestamp very much suggests that it’s referring to an explicit representation of some sort. “timepoint” would be much better for what you’re talking about. Not a criticism of you of course! I mostly write python at work so I rarely am directly exposed to the integer offset values, but I know many people use the word “timestamp” to refer to that integer, as opposed to a formatted string. Which also seems like unfortunate terminology, since what is a stamp if not formatted?

[foepys]

You are assuming that timezones don't change ever in relation to UTC. This is wrong. Timezones change all the time.

When I set an alarm for any time in CEST in 2022 and convert this to UTC before saving it, it will very likely ring at the wrong time, simply because CEST will probably not exist by then and be replaced by CET due to the EU getting rid of DST.

[lokedhs]

But an alarm is not supposed to use timestamps. An alarm is set for a certain time in a certain location. In otherwords, a wallclock time. Not a timestamp.