I've been using a pomodoro app that provides a REST API. Through this API, you can query past pomodoros using parameters such as ended_before and ended_after. The response data also contains started_at and ended_at fields.

The values for these fields all look like this: 2022-01-01T07:18:59.000Z. And they are UTC time strings suffixed with a Z. Correctly so, because it indicates this timestring is UTC.

There are fields named local_started_at and local_ended_at. Although those values are clearly not UTC, they are all suffixed with a Z. This confused me a bit at first. (And it seems quite common for people to suffix Z at the end of a time string, regardless of which timezone that time string actually is.)

The default timezone in a Docker container is UTC. The default timezone of AWS is also UTC. (I wrote a script to check just to be sure. But it's actually written somewhere in the documentation.) ⋯