RFC1123和RFC822的日期格式

5. 日期和时间的规范

5.1. 语法

date-time   =  [ day "," ] date time        ; dd mm yy
                                            ;  hh:mm:ss zzz

day         =  "Mon"  / "Tue" /  "Wed"  / "Thu"
            /  "Fri"  / "Sat" /  "Sun"

date        =  1*2DIGIT month 2DIGIT        ; day month year
                                            ;  e.g. 20 Jun 82

month       =  "Jan"  /  "Feb" /  "Mar"  /  "Apr"
            /  "May"  /  "Jun" /  "Jul"  /  "Aug"
            /  "Sep"  /  "Oct" /  "Nov"  /  "Dec"

time        =  hour zone                    ; ANSI and Military

hour        =  2DIGIT ":" 2DIGIT [":" 2DIGIT]
                                            ; 00:00:00 - 23:59:59

zone        =  "UT"  / "GMT"                ; Universal Time
                                            ; North American : UT
            /  "EST" / "EDT"                ;  Eastern:  - 5/ - 4
            /  "CST" / "CDT"                ;  Central:  - 6/ - 5
            /  "MST" / "MDT"                ;  Mountain: - 7/ - 6
            /  "PST" / "PDT"                ;  Pacific:  - 8/ - 7
            /  1ALPHA                       ; Military: Z = UT;
                                            ;  A:-1; (J not used)
                                            ;  M:-12; N:+1; Y:+12
            / ( ("+" / "-") 4DIGIT )        ; Local differential
                                            ;  hours+min. (HHMM)

5.2. 语义

原文：

     If included, day-of-week must be the day implied by the date
specification.

     Time zone may be indicated in several ways.  "UT" is Univer-
sal  Time  (formerly called "Greenwich Mean Time"); "GMT" is per-
mitted as a reference to Universal Time.  The  military  standard
uses  a  single  character for each zone.  "Z" is Universal Time.
"A" indicates one hour earlier, and "M" indicates 12  hours  ear-
lier;  "N"  is  one  hour  later, and "Y" is 12 hours later.  The
letter "J" is not used.  The other remaining two forms are  taken
from ANSI standard X3.51-1975.  One allows explicit indication of
the amount of offset from UT; the other uses  common  3-character
strings for indicating time zones in North America.

翻译：

参考文档：https://tools.ietf.org/html/rfc822#section-5