LeapSecondTable inverse bug?

[jamesdbrock]

After applying @kim 's patch for #38 to load a LeapSecondTable, I see this.

Lookup UTC -> TAI

> leapSecondTable $ Left $ mkUTCTime (fromGregorian 2015 6 30) (hhmmss 23 59 59)
35s

Lookup (UTC -> TAI) -> UTC

> leapSecondTable $ Right $ mkUTCTime (fromGregorian 2015 6 30) (hhmmss 23 59 59) ^. absoluteTime leapSecondTable 
36s

I think both expressions should return 35s? Is this a bug?

[jamesdbrock]

Here is a better explanation.

$ stack ghci --package http-conduit --package thyme
> :module + Data.Thyme Data.Thyme.Clock.TAI Data.Thyme.Time.Core Network.HTTP.Conduit Data.ByteString.Lazy Control.Lens Data.AffineSpace
> leapSecondTable <- parseTAIUTCDAT . toStrict <$> simpleHttp "http://maia.usno.navy.mil/ser7/tai-utc.dat"
> Prelude.putStrLn $ unlines $ fmap (\t -> show t ++ " = " ++ show (absoluteTime leapSecondTable # t)) $ Prelude.take 10 $ Prelude.iterate (.+^ fromSeconds' 0.2) $ mkUTCTime (fromGregorian 2015 6 30) (hhmmss 23 58 48) ^. absoluteTime leapSecondTable
2015-06-30 23:59:23.0 TAI = 2015-06-30 23:58:48.0 UTC
2015-06-30 23:59:23.2 TAI = 2015-06-30 23:58:48.2 UTC
2015-06-30 23:59:23.4 TAI = 2015-06-30 23:58:48.4 UTC
2015-06-30 23:59:23.6 TAI = 2015-06-30 23:58:48.6 UTC
2015-06-30 23:59:23.8 TAI = 2015-06-30 23:58:48.8 UTC
2015-06-30 23:59:24.0 TAI = 2015-06-30 23:58:48.0 UTC
2015-06-30 23:59:24.2 TAI = 2015-06-30 23:58:48.2 UTC
2015-06-30 23:59:24.4 TAI = 2015-06-30 23:58:48.4 UTC
2015-06-30 23:59:24.6 TAI = 2015-06-30 23:58:48.6 UTC
2015-06-30 23:59:24.8 TAI = 2015-06-30 23:58:48.8 UTC

As we increment TAI you can see the that the UTC leap second transition occurs at 2015-06-30 23:58:48.0 UTC, but I'm pretty sure it's supposed to occur at 2015-06-30 23:59:60.0 UTC.

[jamesdbrock]

Iterating UTC and watching TAI, however, looks good, the UTC transition occurs at 2015-07-01 00:00:00.0 UTC.

> Prelude.putStrLn $ unlines $ fmap (\t -> show t ++ " = " ++ show (t ^. absoluteTime leapSecondTable)) $ Prelude.take 9 $ Prelude.iterate (.+^ fromSeconds' 0.1) $ mkUTCTime (fromGregorian 2015 6 30) (hhmmss 23 59 59.6)
2015-06-30 23:59:59.6 UTC = 2015-07-01 00:00:34.6 TAI
2015-06-30 23:59:59.7 UTC = 2015-07-01 00:00:34.7 TAI
2015-06-30 23:59:59.8 UTC = 2015-07-01 00:00:34.8 TAI
2015-06-30 23:59:59.9 UTC = 2015-07-01 00:00:34.9 TAI
2015-07-01 00:00:00.0 UTC = 2015-07-01 00:00:36.0 TAI
2015-07-01 00:00:00.1 UTC = 2015-07-01 00:00:36.1 TAI
2015-07-01 00:00:00.2 UTC = 2015-07-01 00:00:36.2 TAI
2015-07-01 00:00:00.3 UTC = 2015-07-01 00:00:36.3 TAI
2015-07-01 00:00:00.4 UTC = 2015-07-01 00:00:36.4 TAI

[jamesdbrock]

Oh, of course the reason why this behavior is weird is that Data.Thyme.UTCTime doesn't support leap seconds.

[liyang]

Actually the whole thing is buggy. :-/ There will be a fix soon.