| Portability | portable |
|---|---|
| Maintainer | Yitzchak Gale <gale@sefer.org> |
| Safe Haskell | None |
Data.Time.LocalTime.TimeZone.Series
Contents
Description
A TimeZoneSeries describes a timezone by specifying the various
clock settings that occurred in the past and are scheduled to occur
in the future for the timezone.
- data TimeZoneSeries = TimeZoneSeries {
- tzsTimeZone :: TimeZone
- tzsTransitions :: [(UTCTime, TimeZone)]
- timeZoneFromSeries :: TimeZoneSeries -> UTCTime -> TimeZone
- isValidLocalTime :: TimeZoneSeries -> LocalTime -> Bool
- isRedundantLocalTime :: TimeZoneSeries -> LocalTime -> Bool
- latestNonSummer :: TimeZoneSeries -> TimeZone
- utcToLocalTime' :: TimeZoneSeries -> UTCTime -> LocalTime
- localTimeToUTC' :: TimeZoneSeries -> LocalTime -> UTCTime
- data ZoneSeriesTime = ZoneSeriesTime {}
- zonedTimeToZoneSeriesTime :: ZonedTime -> ZoneSeriesTime
- zoneSeriesTimeToLocalTime :: ZoneSeriesTime -> LocalTime
- zoneSeriesTimeZone :: ZoneSeriesTime -> TimeZone
- localTimeToZoneSeriesTime :: TimeZoneSeries -> LocalTime -> ZoneSeriesTime
Representing a timezone
A TimeZoneSeries describes a timezone with a set of TimeZone
objects. Each TimeZone object describes the clock setting in the
timezone for a specific period of history during which the clocks
do not change.
Most operating systems provide information about timezone series for the local timezone and for many other timezones of the world. On MS Windows systems, this information can be read from the registry. On other systems, this information is typically provided in the form of Olson timezone files: /etc/localtime (or some other file) for the local timezone, and files located in /usr/share/zoneinfo/ or /etc/zoneinfo/ (or some other directory) for other timezones.
data TimeZoneSeries
A TimeZoneSeries consists of a default TimeZone object and a
sequence of pairs of a UTCTime and a TimeZone object. Each
UTCTime indicates a moment at which the clocks changed, and the
corresponding TimeZone object describes the new state of the
clocks after the change. The default TimeZone object is used for
times preceding the earliest UTCTime, or if the sequence of pairs
is empty. The times in the sequence are in order from latest to
earlist (note that this is the opposite of the way that they are
stored in an Olson timezone file).
Constructors
| TimeZoneSeries | |
Fields
| |
timeZoneFromSeries :: TimeZoneSeries -> UTCTime -> TimeZone
Given a timezone represented by a TimeZoneSeries, and a UTCTime,
provide the state of the timezone's clocks at that time.
isValidLocalTime :: TimeZoneSeries -> LocalTime -> Bool
When a clock change moves the clock forward, local times that are between the wall clock time before the change and the wall clock time after the change cannot occur.
isRedundantLocalTime :: TimeZoneSeries -> LocalTime -> Bool
When a clock change moves the clock backward, local times that are between the wall clock time before the change and the wall clock time after the change occur twice.
latestNonSummer :: TimeZoneSeries -> TimeZone
The latest non-summer TimeZone in a TimeZoneSeries is in some
sense representative of the timezone.
Converting between UTC and local time
The following functions are variants on functions in
Data.Time.LocalTime that convert between UTC and local time. The
originals can give a wrong result if the TimeZone used for the
conversion is not actually in effect at the specified time. These
variants use a TimeZoneSeries instead of a TimeZone.
When converting from an invalid local time, the local time is
interpreted as if the time change that made it invalid never
happened. When converting from a redundant local time, the latest
possible interpretation is used. Use the functions
isValidLocalTime and isRedundantLocalTime to detect these
conditions.
utcToLocalTime' :: TimeZoneSeries -> UTCTime -> LocalTime
Convert a UTC time to local time using the TimeZone that is in effect at that time in the timezone represented by TimeZoneSeries.
localTimeToUTC' :: TimeZoneSeries -> LocalTime -> UTCTime
Convert a local time to UTC using the TimeZone that is in effect at that time in the timezone represented by TimeZoneSeries. Local times that are invalid or redundant are treated as described above.
Representing a moment in a timezone
data ZoneSeriesTime
A ZoneSeriesTime represents a moment of time in the context of
a particular timezone.
Constructors
| ZoneSeriesTime | |
Fields | |
zonedTimeToZoneSeriesTime :: ZonedTime -> ZoneSeriesTime
Use a trivial TimeZoneSeries containing only the TimeZone
of the ZonedTime, and use it to define a ZoneSeriesTime.
zoneSeriesTimeToLocalTime :: ZoneSeriesTime -> LocalTime
The local time represented by a ZoneSeriesTime
zoneSeriesTimeZone :: ZoneSeriesTime -> TimeZone
The TimeZone that is in effect at the moment represented by
a ZoneSeriesTime.
localTimeToZoneSeriesTime :: TimeZoneSeries -> LocalTime -> ZoneSeriesTime
The ZoneSeriesTime that represents the given local time in the
given timezone. Local times that are invalid or redundant are treated
as described below.