Daylight savings conversion error

[brianmay]

Steps to reproduce

iex(14)> Timex.Timezone.convert(~U[2021-04-03 15:30:00Z], "Australia/Melbourne")
#DateTime<2021-04-04 01:30:00+10:00 AEST Australia/Melbourne>

Description of issue

This is wrong, it shows the non-daylight savings time.

But daylight savings doesn't end here until 3am local time. Or 16:00 UTC time. Clearly 15:30Z is before 16:00Z. So I would expect that the output should be:

iex(14)> Timex.Timezone.convert(~U[2021-04-03 15:30:00Z], "Australia/Melbourne")
#DateTime<2021-04-04 02:30:00+11:00 AEDT Australia/Melbourne>

Examples of correct conversion:

brian@canidae:~$ date +%F_%T -d "2021-04-03T15:30Z"
2021-04-04_02:30:00

iex(13)> DateTime.shift_zone(~U[2021-04-03 15:30:00Z], "Australia/Melbourne")
{:ok, #DateTime<2021-04-04 02:30:00+11:00 AEDT Australia/Melbourne>}

https://www.timeanddate.com/worldclock/converter.html?iso=20210403T153000&p1=152&p2=1440

The fact that the DateTime library gets the correct value would suggest to me that the error is in the Timex library as opposed to the tzdata database.

[brianmay]

This shows the correct transition from AEDT (day light savings time) to AEST (standard time). Ignore the fact the times are croseed out: https://www.timeanddate.com/worldclock/meetingtime.html?day=4&month=4&year=2021&p1=152&iv=1200

[brianmay]

I forgot to say, this was timex version 3.7.3.

[bitwalker]

There were a few issues in the first few build versions of the 3.7.x series, have you tried again with the latest? Specifically, Timex.to_datetime(~U[2021-04-03 15:30:00Z], "Australia/Melbourne") produces the correct result as expected, as does DateTime.shift_zone/3 if you use Timex.Timezone.Database as the timezone database.

Using Timex.Timezone.convert isn't really intended as a public API, and using it directly like this is not the correct way to handle timezone conversions, despite the name, instead use one of the two options I mentioned above. Make sure you are using version 3.7.5.

[brianmay]

Ooops. Sorry, looks like I made two mistakes:

1. Contrary to what I said above, was using timex version 3.6.4. Getting confused with elixir dependancies.
2. Got the wrong API for the test case. But the problem did occur with public API too.

I can't find any problems after upgrading to 3.7.5, so looks like it was fixed, and you were right to close it.

Thanks.