Then please use proper formatting instead of relying on debug output that may change without a warning at any point in time.

If you want to format a time for presentation use Timex.format, the inspection output is for debugging only and might change its presentation without any warnings.

Hmm, as per the documentation I linked I don’t see why this wouldn’t work for you based on the information given?

iex(1)> Timex.format(DateTime.from_unix!(1549385336000000, :microsecond), "%FT%T.%f%z", :strftime)
{:ok, "2019-02-05T16:48:56.000000+0000"}
iex(2)> Timex.format(DateTime.from_unix!(1549385336000001, :microsecond), "%FT%T.%f%z", :strftime)
{:ok, "2019-02-05T16:48:56.000001+0000"}

Oh! Then my snippet should work perfectly for it as it always prints microseconds, even out to full 0’s if the datetime doesn’t contain them. You really don’t want to change a time to print out for something else, you’d be surprised by the bugs that can happen. ^.^

Can you give a more complete example about how you create the dates and how you convert them?