Documentation about Read/Show instances of TimeZone (#28)

lib/Data/Time/Format/Locale.hs

@@ -32,7 +32,7 @@ data TimeLocale = TimeLocale {
 --
 -- 'knownTimeZones' contains only the ten time-zones mentioned in RFC 822 sec. 5:
 -- \"UT\", \"GMT\", \"EST\", \"EDT\", \"CST\", \"CDT\", \"MST\", \"MDT\", \"PST\", \"PDT\".
--- Note that the parsing functions will regardless parse "UTC", single-letter military time-zones, and +HHMM format.
+-- Note that the parsing functions will regardless parse \"UTC\", single-letter military time-zones, and +HHMM format.
 defaultTimeLocale :: TimeLocale
 defaultTimeLocale =  TimeLocale {
         wDays  = [("Sunday",   "Sun"),  ("Monday",    "Mon"),

lib/Data/Time/Format/Parse.hs

@@ -157,9 +157,15 @@ instance Read TimeOfDay where
 instance Read LocalTime where
     readsPrec _ = readParen False $ readSTime True defaultTimeLocale "%Y-%m-%d %H:%M:%S%Q"
 
+-- | This only works for @±HHMM@ format,
+-- single-letter military time-zones,
+-- and these time-zones: \"UTC\", \"UT\", \"GMT\", \"EST\", \"EDT\", \"CST\", \"CDT\", \"MST\", \"MDT\", \"PST\", \"PDT\".
 instance Read TimeZone where
     readsPrec _ = readParen False $ readSTime True defaultTimeLocale "%Z"
 
+-- | This only works for a 'zonedTimeZone' in @±HHMM@ format,
+-- single-letter military time-zones,
+-- and these time-zones: \"UTC\", \"UT\", \"GMT\", \"EST\", \"EDT\", \"CST\", \"CDT\", \"MST\", \"MDT\", \"PST\", \"PDT\".
 instance Read ZonedTime where
     readsPrec n = readParen False $ \s ->
         [(ZonedTime t z, r2) | (t,r1) <- readsPrec n s, (z,r2) <- readsPrec n r1]

lib/Data/Time/LocalTime/Internal/TimeZone.hs

@@ -67,6 +67,7 @@ timeZoneOffsetString' (Just c) = timeZoneOffsetString'' False $ Pad 4 c
 timeZoneOffsetString :: TimeZone -> String
 timeZoneOffsetString = timeZoneOffsetString'' False (Pad 4 '0')
 
+-- | This only shows the time zone name, or offset if the name is empty.
 instance Show TimeZone where
     show zone@(TimeZone _ _ "") = timeZoneOffsetString zone
     show (TimeZone _ _ name) = name