Thank you ; it’s kind of you to write such a thoughtful, thorough reply.
In my original comment, when I wrote timezone, I actually didn’t really mean one of many known civil timezones (because it’s not), but I meant “timezone string configuration in Linux that will then give TAI time, ie stop adjusting it with timezones, daylight savings, or leap seconds”.
I hadn’t heard of the concept of timescale.
Personally i think item (3) is worthless for computer (as opposed to human facing) timekeeping.
Your explanation is very educational, thank you.
That said, you say it’s simple to get TAI, but that’s within a programming language. What we need is a way to explicitly specify the meaning of a time (timezone but also timescale, I’m learning), and that that interpretation is stored together with the timestamp.
I still don’t understand why a TZ=TAI would be so unreasonable or hard to implement as a shorthand for this desire..
I’m thinking particularly of it being attractive for logfiles and other long term data with time info in it.
I did this for my systems a while ago. You can grab <https://imu.li/TAI.zone>, compile it with the tzdata tools, and stick it in /etc/zoneinfo. It is unfortunately unable to keep time during a leap second.
In theory, if you keep your clock set to TAI instead of UTC, you can use the /etc/zoneinfo/right timezones for civic time and make a (simpler) TAI zone file. I learned of that after I'd created the above though, and I can imagine all sorts of problems with getting the NTP daemon to do the right thing, and my use case was more TZ=TAI date, as you mentioned.
There's a contentious discussion on the time zone mailing list about adding a TAI entry. It really didn't help that DJB was the one wanting to add it and approached the issue with his customary attitude. There's a lot of interesting stuff in there though - like allegedly there's a legal requirement in Germany for their time zone to be fixed to the rotation of the earth (and so they might abandon UTC if it gives up leap seconds).
In my original comment, when I wrote timezone, I actually didn’t really mean one of many known civil timezones (because it’s not), but I meant “timezone string configuration in Linux that will then give TAI time, ie stop adjusting it with timezones, daylight savings, or leap seconds”.
I hadn’t heard of the concept of timescale.
Personally i think item (3) is worthless for computer (as opposed to human facing) timekeeping.
Your explanation is very educational, thank you.
That said, you say it’s simple to get TAI, but that’s within a programming language. What we need is a way to explicitly specify the meaning of a time (timezone but also timescale, I’m learning), and that that interpretation is stored together with the timestamp.
I still don’t understand why a TZ=TAI would be so unreasonable or hard to implement as a shorthand for this desire..
I’m thinking particularly of it being attractive for logfiles and other long term data with time info in it.