インターネット上での日付と時刻：タイムスタンプ（参照と安全）

   [ZELLER]       Zeller, C., "Kalender-Formeln", Acta Mathematica, Vol.
                  9, Nov 1886.

   [IMAIL]        Crocker, D., "Standard for the Format of Arpa Internet
                  Text Messages", STD 11, RFC 822, August 1982.

   [IMAIL-UPDATE] Resnick, P., "Internet Message Format", RFC 2822,
                  April 2001.

   [ABNF]         Crocker, D. and P. Overell, "Augmented BNF for Syntax
                  Specifications: ABNF", RFC 2234, November 1997.

   [ISO8601]      "Data elements and interchange formats -- Information
                  interchange -- Representation of dates and times", ISO
                  8601:1988(E), International Organization for
                  Standardization, June, 1988.

   [ISO8601:2000] "Data elements and interchange formats -- Information
                  interchange -- Representation of dates and times", ISO
                  8601:2000, International Organization for
                  Standardization, December, 2000.

   [HOST-REQ]     Braden, R., "Requirements for Internet Hosts --
                  Application and Support", STD 3, RFC 1123, October
                  1989.

   [IERS]         International Earth Rotation Service Bulletins,
                  <http://hpiers.obspm.fr/eop-
                  pc/products/bulletins.html>.

   [NTP]          Mills, D, "Network Time Protocol (Version 3)
                  Specification, Implementation and Analysis", RFC 1305,
                  March 1992.

   [ITU-R-TF]     International Telecommunication Union Recommendations
                  for Time Signals and Frequency Standards Emissions.
                  <http://www.itu.ch/publications/itu-r/iturtf.htm>

   [RFC2119]      Bradner, S, "Key words for use in RFCs to Indicate
                  Requirement Levels", BCP 14, RFC 2119, March 1997.

   Since the local time zone of a site may be useful for determining a
   time when systems are less likely to be monitored and might be more
   susceptible to a security probe, some sites may wish to emit times in
   UTC only.  Others might consider this to be loss of useful
   functionality at the hands of paranoia.