2
[Extracts from RFC2822]
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3.3. Date and Time Specification
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Date and time occur in several header fields. This section specifies
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the syntax for a full date and time specification. Though folding
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white space is permitted throughout the date-time specification, it
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is RECOMMENDED that a single space be used in each place that FWS
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appears (whether it is required or optional); some older
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implementations may not interpret other occurrences of folding white
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date-time = [ day-of-week "," ] date FWS time [CFWS]
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day-of-week = ([FWS] day-name) / obs-day-of-week
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day-name = "Mon" / "Tue" / "Wed" / "Thu" /
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year = 4*DIGIT / obs-year
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month = (FWS month-name FWS) / obs-month
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month-name = "Jan" / "Feb" / "Mar" / "Apr" /
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"May" / "Jun" / "Jul" / "Aug" /
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"Sep" / "Oct" / "Nov" / "Dec"
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day = ([FWS] 1*2DIGIT) / obs-day
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time = time-of-day FWS zone
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time-of-day = hour ":" minute [ ":" second ]
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hour = 2DIGIT / obs-hour
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minute = 2DIGIT / obs-minute
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second = 2DIGIT / obs-second
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zone = (( "+" / "-" ) 4DIGIT) / obs-zone
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The day is the numeric day of the month. The year is any numeric
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The time-of-day specifies the number of hours, minutes, and
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optionally seconds since midnight of the date indicated.
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The date and time-of-day SHOULD express local time.
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The zone specifies the offset from Coordinated Universal Time (UTC,
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formerly referred to as "Greenwich Mean Time") that the date and
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time-of-day represent. The "+" or "-" indicates whether the
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time-of-day is ahead of (i.e., east of) or behind (i.e., west of)
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Universal Time. The first two digits indicate the number of hours
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difference from Universal Time, and the last two digits indicate the
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number of minutes difference from Universal Time. (Hence, +hhmm
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means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
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minutes). The form "+0000" SHOULD be used to indicate a time zone at
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Universal Time. Though "-0000" also indicates Universal Time, it is
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used to indicate that the time was generated on a system that may be
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in a local time zone other than Universal Time and therefore
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indicates that the date-time contains no information about the local
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A date-time specification MUST be semantically valid. That is, the
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day-of-the-week (if included) MUST be the day implied by the date,
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the numeric day-of-month MUST be between 1 and the number of days
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allowed for the specified month (in the specified year), the
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time-of-day MUST be in the range 00:00:00 through 23:59:60 (the
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number of seconds allowing for a leap second; see [STD12]), and the
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zone MUST be within the range -9959 through +9959.
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4.3. Obsolete Date and Time
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The syntax for the obsolete date format allows a 2 digit year in the
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date field and allows for a list of alphabetic time zone
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specifications that were used in earlier versions of this standard.
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It also permits comments and folding white space between many of the
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obs-day-of-week = [CFWS] day-name [CFWS]
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obs-year = [CFWS] 2*DIGIT [CFWS]
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obs-month = CFWS month-name CFWS
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obs-day = [CFWS] 1*2DIGIT [CFWS]
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obs-hour = [CFWS] 2DIGIT [CFWS]
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obs-minute = [CFWS] 2DIGIT [CFWS]
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obs-second = [CFWS] 2DIGIT [CFWS]
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obs-zone = "UT" / "GMT" / ; Universal Time
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"EST" / "EDT" / ; Eastern: - 5/ - 4
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"CST" / "CDT" / ; Central: - 6/ - 5
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"MST" / "MDT" / ; Mountain: - 7/ - 6
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"PST" / "PDT" / ; Pacific: - 8/ - 7
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%d65-73 / ; Military zones - "A"
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%d75-90 / ; through "I" and "K"
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%d97-105 / ; through "Z", both
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%d107-122 ; upper and lower case
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Where a two or three digit year occurs in a date, the year is to be
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interpreted as follows: If a two digit year is encountered whose
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value is between 00 and 49, the year is interpreted by adding 2000,
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ending up with a value between 2000 and 2049. If a two digit year is
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encountered with a value between 50 and 99, or any three digit year
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is encountered, the year is interpreted by adding 1900.
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In the obsolete time zone, "UT" and "GMT" are indications of
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"Universal Time" and "Greenwich Mean Time" respectively and are both
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semantically identical to "+0000".
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The remaining three character zones are the US time zones. The first
127
letter, "E", "C", "M", or "P" stands for "Eastern", "Central",
128
"Mountain" and "Pacific". The second letter is either "S" for
129
"Standard" time, or "D" for "Daylight" (or summer) time. Their
130
interpretations are as follows:
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EDT is semantically equivalent to -0400
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EST is semantically equivalent to -0500
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CDT is semantically equivalent to -0500
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CST is semantically equivalent to -0600
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MDT is semantically equivalent to -0600
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MST is semantically equivalent to -0700
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PDT is semantically equivalent to -0700
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PST is semantically equivalent to -0800
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The 1 character military time zones were defined in a non-standard
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way in [RFC822] and are therefore unpredictable in their meaning.
143
The original definitions of the military zones "A" through "I" are
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equivalent to "+0100" through "+0900" respectively; "K", "L", and "M"
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are equivalent to "+1000", "+1100", and "+1200" respectively; "N"
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through "Y" are equivalent to "-0100" through "-1200" respectively;
147
and "Z" is equivalent to "+0000". However, because of the error in
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[RFC822], they SHOULD all be considered equivalent to "-0000" unless
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there is out-of-band information confirming their meaning.
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Other multi-character (usually between 3 and 5) alphabetic time zones
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have been used in Internet messages. Any such time zone whose
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meaning is not known SHOULD be considered equivalent to "-0000"
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unless there is out-of-band information confirming their meaning.
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Appendix B. Differences from earlier standards
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This appendix contains a list of changes that have been made in the
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Internet Message Format from earlier standards, specifically [RFC822]
162
and [STD3]. Items marked with an asterisk (*) below are items which
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appear in section 4 of this document and therefore can no longer be
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1. Period allowed in obsolete form of phrase.
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2. ABNF moved out of document to [RFC2234].
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3. Four or more digits allowed for year.
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4. Header field ordering (and lack thereof) made explicit.
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5. Encrypted header field removed.
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6. Received syntax loosened to allow any token/value pair.
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7. Specifically allow and give meaning to "-0000" time zone.
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8. Folding white space is not allowed between every token.
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9. Requirement for destinations removed.
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10. Forwarding and resending redefined.
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11. Extension header fields no longer specifically called out.
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12. ASCII 0 (null) removed.*
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13. Folding continuation lines cannot contain only white space.*
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14. Free insertion of comments not allowed in date.*
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15. Non-numeric time zones not allowed.*
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16. Two digit years not allowed.*
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17. Three digit years interpreted, but not allowed for generation.
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18. Routes in addresses not allowed.*
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19. CFWS within local-parts and domains not allowed.*
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20. Empty members of address lists not allowed.*
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21. Folding white space between field name and colon not allowed.*
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22. Comments between field name and colon not allowed.
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23. Tightened syntax of in-reply-to and references.*
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24. CFWS within msg-id not allowed.*
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25. Tightened semantics of resent fields as informational only.
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26. Resent-Reply-To not allowed.*
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27. No multiple occurrences of fields (except resent and received).*
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28. Free CR and LF not allowed.*
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29. Routes in return path not allowed.*
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30. Line length limits specified.
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31. Bcc more clearly specified.
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Full Copyright Statement
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Copyright (C) The Internet Society (2001). All Rights Reserved.
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This document and translations of it may be copied and furnished to
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others, and derivative works that comment on or otherwise explain it
206
or assist in its implementation may be prepared, copied, published
207
and distributed, in whole or in part, without restriction of any
208
kind, provided that the above copyright notice and this paragraph are
209
included on all such copies and derivative works. However, this
210
document itself may not be modified in any way, such as by removing
211
the copyright notice or references to the Internet Society or other
212
Internet organizations, except as needed for the purpose of
213
developing Internet standards in which case the procedures for
214
copyrights defined in the Internet Standards process must be
215
followed, or as required to translate it into languages other than
218
The limited permissions granted above are perpetual and will not be
219
revoked by the Internet Society or its successors or assigns.
221
This document and the information contained herein is provided on an
222
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
224
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
225
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
226
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