unix-time test fails about stackage

[snoyberg]

@kazu-yamamoto Any ideas? Should I add unix-time back to the expected failures list?

[kazu-yamamoto]

@byorgey Would you do the following sequence?

% cd tests
% ghci UnixTimeSpec.hs
> let ut = UnixTime {utSeconds = 1571502693, utMicroSeconds = 548856}
> formatUnixTime mailDateFormat ut
"Sun, 20 Oct 2019 01:31:33 +0900"
> currentTimeZone <- getCurrentTimeZone
> formatMailModel (toUTCTime ut) currentTimeZone
"Sun, 20 Oct 2019 01:31:33 +0900"

And please tell me what kinds of results are returned.
In the case above, the results are the same. So, it should pass the test.

[byorgey]

*UnixTimeSpec> let ut = UnixTime {utSeconds = 1571502693, utMicroSeconds = 548856}
*UnixTimeSpec> formatUnixTime mailDateFormat ut
"Sat, 19 Oct 2019 12:31:33 -0400"
*UnixTimeSpec> currentTimeZone <- getCurrentTimeZone
*UnixTimeSpec> formatMailModel (toUTCTime ut) currentTimeZone
"Sat, 19 Oct 2019 11:31:33 -0500"

[kazu-yamamoto]

Which time zone is correct?

[byorgey]

Oh, I see the problem. On 19 Oct 2019, Daylight Saving Time would be in effect, hence the correct time zone would be -0400 (EDT). However, currently DST is not in effect so the time zone is -0500 (EST). The time zone is date-dependent, hence it is not correct to use currentTimeZone with arbitrary dates.

[kazu-yamamoto]

So, what would you suggest to solve this problem? What can I do for this?

[byorgey]

The only way I know of to solve this in a completely correct way would be to use http://hackage.haskell.org/package/timezone-series and http://hackage.haskell.org/package/timezone-olson . However, that involves pulling two more packages into stackage and in any case Olson files may not even be available on every platform. I don't know if it is worth it.

[kazu-yamamoto]

@snoyberg Would you add unix-time to the expected failures list?

[snoyberg]

@kazu-yamamoto Done

[snoyberg]

OK, since the unix-time test failures no longer affect Stackage, I'm closing this issue. If something in unix-time still needs to be tweaked (I'm not sure based on the above conversation), let's move discussion to unix-time itself.