+-- |This module provides functions to parse and format RFC 822 date
+-- and time formats.
+--
+-- The syntax is as follows:
+--
+-- > date-time ::= [ day-of-week ", " ] date SP time SP zone
+-- > day-of-week ::= "Mon" | "Tue" | "Wed" | "Thu"
+-- > | "Fri" | "Sat" | "Sun"
+-- > date ::= day SP month SP year
+-- > day ::= 2DIGIT
+-- > year ::= 2DIGIT ; Yes, only 2 digits.
+-- > month ::= "Jan" | "Feb" | "Mar" | "Apr"
+-- > | "May" | "Jun" | "Jul" | "Aug"
+-- > | "Sep" | "Oct" | "Nov" | "Dec"
+-- > time ::= hour ":" minute [ ":" second ]
+-- > hour ::= 2DIGIT
+-- > minute ::= 2DIGIT
+-- > second ::= 2DIGIT
+-- > zone ::= "UT" | "GMT" ; Universal Time
+-- > | "EST" | "EDT" ; Eastern : -5 / -4
+-- > | "CST" | "CDT" ; Central : -6 / -5
+-- > | "MST" | "MDT" ; Mountain: -7 / -6
+-- > | "PST" | "PDT" ; Pacific : -8 / -7
+-- > | "Z" ; UT
+-- > | "A" ; -1
+-- > | "M" ; -12
+-- > | "N" ; +1
+-- > | "Y" ; +12
+-- > | ("+" | "-") 4DIGIT ; Local diff: HHMM