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     ctime, localtime, gmtime  -  convert date and time to ASCII

     char *ctime(tvec)
     int tvec[2];

     [from Fortran]
     double precision ctime

     int *localtime(tvec)
     int tvec[2];

     int *gmtime(tvec)
     int tvec[2];

     Ctime converts a time in the vector tvec such as returned by
     time (II) into ASCII and returns a pointer to a character
     string in the form

         Sun Sep 16 01:03:52 1973\n\0

     All the fields have constant width.

     The localtime and gmtime entries return pointers to integer
     vectors containing the broken-down time.  Localtime corrects
     for the time zone and possible daylight savings time; gmtime
     converts directly to GMT, which is the time UNIX uses.  The
     value is a pointer to an array whose components are

     0    seconds
     1    minutes
     2    hours
     3    day of the month (1-31)
     4    month (0-11)
     5    year - 1900
     6    day of the week (Sunday = 0)
     7    day of the year (0-365)
     8    Daylight Saving Time flag if non-zero

     The external variable timezone contains the difference, in
     seconds, between GMT and local standard time (in EST, is
     5*60*60); the external variable daylight is non-zero iff the
     standard U.S.A. Daylight Savings Time conversion should be
     applied.  The program knows about the peculiarities of this
     conversion in 1974 and 1975; if necessary, a table for these
     years can be extended.

     A routine named ctime is also available from Fortran.  Actu-
     ally it more resembles the time (II) system entry in that it
     returns the number of seconds since the epoch 0000 GMT Jan.
     1, 1970 (as a floating-point number).