Characters other than those in the "reserved" and "unsafe" sets (see
   section 3.2) are equivalent to their ""%" HEX HEX" encodings.

   For example, the following three URIs are equivalent:

         http://abc.com:80/~smith/home.html
         http://ABC.com/%7Esmith/home.html
         http://ABC.com:/%7esmith/home.html













 
RFC 2068                        HTTP/1.1                    January 1997


3.3 Date/Time Formats

3.3.1 Full Date

   HTTP applications have historically allowed three different formats
   for the representation of date/time stamps:

          Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123
          Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036
          Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format

   The first format is preferred as an Internet standard and represents
   a fixed-length subset of that defined by RFC 1123  (an update to RFC
   822).  The second format is in common use, but is based on the
   obsolete RFC 850 [12] date format and lacks a four-digit year.
   HTTP/1.1 clients and servers that parse the date value MUST accept
   all three formats (for compatibility with HTTP/1.0), though they MUST
   only generate the RFC 1123 format for representing HTTP-date values
   in header fields.

     Note: Recipients of date values are encouraged to be robust in
     accepting date values that may have been sent by non-HTTP
     applications, as is sometimes the case when retrieving or posting
     messages via proxies/gateways to SMTP or NNTP.

   All HTTP date/time stamps MUST be represented in Greenwich Mean Time
   (GMT), without exception. This is indicated in the first two formats
   by the inclusion of "GMT" as the three-letter abbreviation for time
   zone, and MUST be assumed when reading the asctime format.

          HTTP-date    = rfc1123-date | rfc850-date | asctime-date

          rfc1123-date = wkday "," SP date1 SP time SP "GMT"
          rfc850-date  = weekday "," SP date2 SP time SP "GMT"
          asctime-date = wkday SP date3 SP time SP 4DIGIT

          date1        = 2DIGIT SP month SP 4DIGIT
                         ; day month year (e.g., 02 Jun 1982)
          date2        = 2DIGIT "-" month "-" 2DIGIT
                         ; day-month-year (e.g., 02-Jun-82)
          date3        = month SP ( 2DIGIT | ( SP 1DIGIT ))
                         ; month day (e.g., Jun  2)

          time         = 2DIGIT ":" 2DIGIT ":" 2DIGIT
                         ; 00:00:00 - 23:59:59

          wkday        = "Mon" | "Tue" | "Wed"
                       | "Thu" | "Fri" | "Sat" | "Sun"




 
RFC 2068                        HTTP/1.1                    January 1997


          weekday      = "Monday" | "Tuesday" | "Wednesday"
                       | "Thursday" | "Friday" | "Saturday" | "Sunday"

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

     Note: HTTP requirements for the date/time stamp format apply only
     to their usage within the protocol stream. Clients and servers are
     not required to use these formats for user presentation, request
     logging, etc.

3.3.2 Delta Seconds

   Some HTTP header fields allow a time value to be specified as an
   integer number of seconds, represented in decimal, after the time
   that the message was received.