NAME
       clock - Obtain and manipulate time

SYNOPSIS
       clock option ?arg arg ...?


DESCRIPTION
       This  command  performs  one  of  several operations that may obtain or
       manipulate strings or values that represent some notion of  time.   The
       option  argument  determines what action is carried out by the command.
       The legal options (which may be abbreviated) are:

       clock clicks ?-milliseconds?
              Return a high-resolution time value as a system-dependent  inte-
              ger value.  The unit of the value is system-dependent but should
              be the highest resolution clock available on the system such  as
              a  CPU  cycle  counter.  If -milliseconds is specified, then the
              value is guaranteed to  be  of  millisecond  granularity.   This
              value  should  only  be  used  for  the  relative measurement of
              elapsed time.

       clock format clockValue ?-format string? ?-gmt boolean?
              Converts an integer time value, typically returned by clock sec-
              onds, clock scan, or the atime or mtime options of the file com-
              mand, to  human-readable  form.   If  the  -format  argument  is
              present  the  next  argument  is a string that describes how the
              date and time are to be formatted.  Field descriptors consist of
              a % followed by a field descriptor character.  All other charac-
              ters are copied into the result.  Valid field descriptors are:

              %%     Insert a %.

              %a     Abbreviated weekday name (Mon, Tue, etc.).

              %A     Full weekday name (Monday, Tuesday, etc.).

              %b     Abbreviated month name (Jan, Feb, etc.).

              %B     Full month name.

              %c     Locale specific date and time.  The format for  date  and
                     time  in  the default "C" locale on Unix/Mac is "%a %b %d
                     %H:%M:%S %Y".  On Windows, this value is the locale  spe-
                     cific  long  date  and time, as specified in the Regional
                     Options control panel settings.

              %C     First two digits of the four-digit year (19 or 20).

              %d     Day of month (01 - 31).

              %D     Date as %m/%d/%y.

              %e     Day of month (1 - 31), no leading zeros.

              %g     The ISO8601 year number corresponding to the ISO8601 week
                     (%V),  expressed as a two-digit year-of-the-century, with
                     leading zero if necessary.

              %G     The ISO8601 year number corresponding to the ISO8601 week
                     (%V), expressed as a four-digit number.

              %h     Abbreviated month name.

              %H     Hour in 24-hour format (00 - 23).

              %I     Hour in 12-hour format (01 - 12).

              %j     Day of year (001 - 366).

              %k     Hour in 24-hour format, without leading zeros (0 - 23).

              %l     Hour in 12-hour format, without leading zeros (1 - 12).

              %m     Month number (01 - 12).

              %M     Minute (00 - 59).

              %n     Insert a newline.

              %p     AM/PM indicator.

              %r     Time in a locale-specific "meridian" format.  The "merid-
                     ian" format in the default "C" locale is "%I:%M:%S %p".

              %R     Time as %H:%M.

              %s     Count of seconds since the epoch, expressed as a  decimal
                     integer.

              %S     Seconds (00 - 59).

              %t     Insert a tab.

              %T     Time as %H:%M:%S.

              %u     Weekday number (Monday = 1, Sunday = 7).

              %U     Week  of  year  (00 - 52), Sunday is the first day of the
                     week.

              %V     Week of year according to ISO-8601 rules.  Week  1  of  a
                     given year is the week containing 4 January.

              %w     Weekday number (Sunday = 0, Saturday = 6).

              %W     Week  of  year  (00 - 52), Monday is the first day of the
                     week.

              %x     Locale specific date format.  The format for  a  date  in
                     the  default  "C"  locale for Unix/Mac is "%m/%d/%y".  On
                     Windows, this value is the  locale  specific  short  date
                     format,  as  specified  in  the  Regional Options control
                     panel settings.

              %X     Locale specific 24-hour time format.  The  format  for  a
                     24-hour  time  in  the default "C" locale for Unix/Mac is
                     "%H:%M:%S".  On Windows, this value is  the  locale  spe-
                     cific  time  format, as specified in the Regional Options
                     control panel settings.

              %y     Year without century (00 - 99).

              %Y     Year with century (e.g. 1990)

              %Z     Time zone name.

              If the -format argument is not specified, the format string  "%a
              %b  %d %H:%M:%S %Z %Y" is used.  If the -gmt argument is present
              the next argument must be a boolean which if true specifies that
              the time will be formatted as Greenwich Mean Time. If false then
              the local timezone will be used  as  defined  by  the  operating
              environment.

       clock scan dateString ?-base clockVal? ?-gmt boolean?
              Convert  dateString  to  an  integer clock value (see clock sec-
              onds).  This command can parse and convert virtually  any  stan-
              dard  date  and/or  time string, which can include standard time
              zone mnemonics.  If only a time is specified, the  current  date
              is  assumed.   If  the  string  does  not  contain  a  time zone
              mnemonic, the local time zone is assumed, unless the -gmt  argu-
              ment is true, in which case the clock value is calculated assum-
              ing that the specified time is relative to Greenwich Mean  Time.
              -gmt,  if  specified,  affects  only the computed time value; it
              does not impact the interpretation of -base.

              If the -base flag is specified, the next argument should contain
              an  integer  clock  value.  Only the date in this value is used,
              not the time.  This is useful for determining the time on a spe-
              cific day or doing other date-relative conversions.

              The  dateString  consists  of zero or more specifications of the
              following form:

              time   A time  of  day,  which  is  of  the  form:  hh?:mm?:ss??
                     ?meridian?  ?zone?  or  hhmm  ?meridian?   ?zone?.  If no
                     meridian is specified, hh is  interpreted  on  a  24-hour
                     clock.

              date   A specific month and day with optional year.  The accept-
                     able formats are mm/dd?/yy?, monthname dd ?, yy?, dd mon-
                     thname ?yy?, day, dd monthname yy, ?CC?yymmdd, ?CC?yy-mm-
                     dd, dd-monthname-?CC?yy.  The default year is the current
                     year.   If  the year is less than 100, we treat the years
                     00-68 as 2000-2068 and the years 69-99 as 1969-1999.  Not
                     all  platforms can represent the years 38-70, so an error
                     may result if these years are used.

              ISO 8601 point-in-time
                     An ISO 8601 point-in-time specification, such as CCyymmd-
                     dThhmmss,  where  T is the literal T, CCyymmdd hhmmss, or
                     CCyymmddThh:mm:ss.  Note that only  these  three  formats
                     are accepted.  The command does not accept the full range
                     of point-in-time  specifications  specified  in  ISO8601.
                     Other formats can be recognized by using commands such as
                     regexp to extract their fields and reorganize them into a
                     form accepted by the clock scan command.

              relative time
                     A specification relative to the current time.  The format
                     is number unit  acceptable  units  are  year,  fortnight,
                     month,  week,  day, hour, minute (or min), and second (or
                     sec).  The unit can be specified as a singular or plural,
                     as  in  3  weeks.  These modifiers may also be specified:
                     tomorrow, yesterday, today, now, last, this, next, ago.

              The actual date is calculated according to the following  steps.
              First, any absolute date and/or time is processed and converted.
              Using that time as  the  base,  day-of-week  specifications  are
              added.   Next,  relative  specifications are used.  If a date or
              day is specified, and no absolute or  relative  time  is  given,
              midnight  is used.  Finally, a correction is applied so that the
              correct hour of the day is produced after allowing for  daylight
              savings  time  differences  and  the  correct date is given when
              going from the end of a long month to a short month.

              Daylight savings time correction is applied only when the  rela-
              tive  time  is  specified  in  units  of days or more, ie, days,
              weeks, fortnights, months or years.  This means that when cross-
              ing  the  daylight savings time boundary, different results will
              be given for clock scan "1 day" and clock scan "24 hours":
                     % clock scan "1 day" -base [clock scan 1999-10-31]
                     941443200
                     % clock scan "24 hours" -base [clock scan 1999-10-31]
                     941439600

       clock seconds
              Return the current date and time as a  system-dependent  integer
              value.  The unit of the value is seconds, allowing it to be used
              for relative time calculations.  The value is usually defined as
              total  elapsed time from an ``epoch''.  You shouldn't assume the
              value of the epoch.


SEE ALSO
       date(1), time(n)


KEYWORDS
