Use of timezones in Jira

[Tim Coote]

Hullo

I believe that a timezone is a geographic region that uses agreed local time. (e.g. Merriam Webster).  An issue with this is that the agreed time can vary over longer periods, thus during the early C20 there was Dutch Time was about 19 and a half minutes ahead of what is now called UTC. At some point daylight saving was also adopted. Confusingly, GMT, which was a time standard, is now a timezone. Even more confusingly, it's not used in Greenwich, which is in the timezone 'Europe/London'

When using time and converting it to another timezone, it is important to know the whole datetime, so that whatever dst conventions had been legislated for can be taken into account. Nowadays, most timezones use an offset in multiples of hours, from UTC for any moment in time, and the offset changes throughout the year.

(I'll ignore the complications of gaps and overlaps in official time that dst introduces, as well as the niceties of leap seconds).

So, a timezone identifies a geographic area. And confusion over the use causes significant issues (I once was involved in identifying all instances of Java libraries in a bank that had the wrong date for changing US DST, so that market opening times could be accurately used.)

However, in Jira, the timezone appears to include a specific time offset from UTC. Is this offset supposed to be the offset for the time referred to, or the baseline offset for a geographic region; leaving the checking of current dst for the timezone as an exercise for the user?  What does it mean if I set my timezone to 'Europe/London +00:00' during the summer for the northern hemisphere? Does it mean that it's actually UTC+01:00, or are my meetings actually in UTC?