Especially in API interfaces, where JSON don't have timestamps type natively. You'll have to represent the timestamp as either a string or a number. Do you prefer to use IOS 8601 (a string) or Unix Epoch (a number), or some other format?
After the poll, can you comment on:
Advantages of timestamp:
Advantages of iso or other readable format:
So I guess it depends: if performance is important I'd favor timestamps, while if humans often read it I'd favor text. (Of course some debuggers will always read it, but more often than not they don't need to know which exact day it represents).
ISO 8601 - purely because, as a human, I can know what date/time it is by eye vs. having to stick it in a unix timestamp converter.
We had that discussion a few time with the team, and we always came back to the same conclusion:
And regarding epoch format (seconds, versus milliseconds), is usually depends on the data itself. When it’s to keep track of human-based interaction (user A did Foo on Bar at this timestamp), using second is perfectly fine. When the goal is to record device activity (we’re an IoT company with a lot of data streams), usually milliseconds is required (when you have a device send 20 values each seconds, it’s just common sense ;-)
As a rule of thumb, I’d say the goal is always to make it as efficient and error-free as possible. (Hence the choice of ISO for the API: as humans write code to call our API, ISO is self-documented and removes all the questions, assumptions, and therefore risks os misuse)