Database.PostgreSQL.Simple.Time

Time types that supports positive and negative infinity. Also includes new time parsers and printers with better performance than GHC's time package.

The parsers only understand the specific variant of ISO 8601 that PostgreSQL emits, and the printers attempt to duplicate this syntax. Thus the datestyle parameter for the connection must be set to ISO.

These parsers and printers likely have problems and shortcomings. Some that I know of:

1 TimestampTZs before a timezone-dependent point in time cannot be parsed, because the parsers can only handle timezone offsets of a integer number of minutes. However, PostgreSQL will include seconds in the offset, depending on the historical time standards for the city identifying the time zone.

This boundary point often marks an event of some interest. In the US for example, timestamptzs before 1883-Nov-18 12:00:00 local time cannot be parsed. This is the moment Standard Railway Time went live. Concretely, PostgreSQL will emit 1883-11-18 12:03:57-04:56:02 instead of 1883-11-18 11:59:59-05 when the timezone parameter for the connection is set to America/New_York.

1. Dates and times surrounding 1582-Feb-24, the date the Gregorian Calendar was introduced, should be investigated for conversion errors.
2. Points in time Before Christ are not also not supported. For example, PostgreSQL will emit 0045-01-01 BC for a value of a date type. This is the year that the Julian Calendar was adopted.

However, it should be noted that the old parsers also had issues 1 and 3. Also, the new parsers now correctly handle time zones that include minutes in their offset. Most notably, this includes all of India and parts of Canada and Australia.

PostgreSQL uses the zoneinfo database for its time zone information. You can read more about PostgreSQL's date and time types at http://www.postgresql.org/docs/9.1/static/datatype-datetime.html, and zoneinfo at http://en.wikipedia.org/wiki/Tz_database.

Documentation

data Unbounded a

Constructors

NegInfinity

Finite !a

PosInfinity

Instances

Typeable1 Unbounded

ToField Date

ToField ZonedTimestamp

ToField UTCTimestamp

ToField LocalTimestamp

FromField Date

date

FromField ZonedTimestamp

timestamptz

FromField UTCTimestamp

timestamptz

FromField LocalTimestamp

timestamp

Eq a => Eq (Unbounded a)

Ord a => Ord (Unbounded a)

Read a => Read (Unbounded a)

Show a => Show (Unbounded a)

type Date = Unbounded Day

type UTCTimestamp = Unbounded UTCTime

type ZonedTimestamp = Unbounded ZonedTime

type LocalTimestamp = Unbounded LocalTime

parseDay :: ByteString -> Either String Day

parseUTCTime :: ByteString -> Either String UTCTime

parseZonedTime :: ByteString -> Either String ZonedTime

parseLocalTime :: ByteString -> Either String LocalTime

parseTimeOfDay :: ByteString -> Either String TimeOfDay

parseDate :: ByteString -> Either String Date

parseUTCTimestamp :: ByteString -> Either String UTCTimestamp

parseZonedTimestamp :: ByteString -> Either String ZonedTimestamp

parseLocalTimestamp :: ByteString -> Either String LocalTimestamp

dayToBuilder :: Day -> Builder

utcTimeToBuilder :: UTCTime -> Builder

zonedTimeToBuilder :: ZonedTime -> Builder

localTimeToBuilder :: LocalTime -> Builder

timeOfDayToBuilder :: TimeOfDay -> Builder

timeZoneToBuilder :: TimeZone -> Builder

dateToBuilder :: Date -> Builder

utcTimestampToBuilder :: UTCTimestamp -> Builder

zonedTimestampToBuilder :: ZonedTimestamp -> Builder

localTimestampToBuilder :: LocalTimestamp -> Builder

unboundedToBuilder :: (a -> Builder) -> Unbounded a -> Builder