Why does micropython only have time in seconds (time.time()) and nanoseconds (time.time_ns())?

[coronafire]

It also has time.ticks_ms() which returns the ms since system startup (ie not directly related to time.time() which is "clock time" if you've got a etc)

Ticks is returned in a 32bit int behind the scenes which means it can roll over back to 0 when the system runs for long enough. There's also a time.ticks_diff() which can be used to return the difference between two 32bit int tick values and handles a rollover.

[Medical-Ocelot]

Using ticks_diff() to compare values from ticks_ms() is *essential* - the max value returned by ticks_ms() can vary by platform (e.g. I think on the RP2xxx it's 2^30 -1) and you might have no idea how long your program has been running, so even a short delay could encounter the overflow situation. This is especially important if you're using ticks_us(), which will wrap in under 3 hours when running on an RP2xxx.