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
              Return  a  high-resolution  time value as a system-
              dependent integer value.  The unit of the value  is
              system-dependent  but should be the highest resolu-
              tion clock available on the system such  as  a  CPU
              cycle  counter.  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 seconds, clock scan, or the atime, mtime,
              or ctime options of the  file  command,  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  characters 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.

              %d     Day of month (01 - 31).

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

              %I     Hour in 12-hour format (00 - 12).

              %j     Day of year (001 - 366).
              %m     Month number (01 - 12).

              %M     Minute (00 - 59).

              %p     AM/PM indicator.

              %S     Seconds (00 - 59).

              %U     Week  of year (01 - 52), Sunday is the first
                     day of the week.

              %w     Weekday number (Sunday = 0).

              %W     Week of year (01 - 52), Monday is the  first
                     day of the week.

              %x     Locale specific date format.

              %X     Locale specific time format.

              %y     Year without century (00 - 99).

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

              %Z     Time zone name.

              In addition, the following field descriptors may be
              supported on some systems (e.g. Unix but  not  Win-
              dows):

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

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

              %h     Abbreviated month name.

              %n     Insert a newline.

              %r     Time as %I:%M:%S %p.

              %R     Time as %H:%M.

              %t     Insert a tab.

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

              If  the -format argument is not specified, the for-
              mat 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 seconds).  This command can parse and convert
              virtually  any  standard  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 argument is true, in which case the
              clock  value is calculated assuming that the speci-
              fied time is relative to Greenwich Mean Time.

              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 specific day
              or doing other date-relative conversions.

              The dateString consists of zero or more  specifica-
              tions 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 speci-
                     fied, hh is interpreted on a 24-hour  clock.

              date   A specific month and day with optional year.
                     The acceptable formats are mm/dd?/yy?,  mon-
                     thname dd ?, yy?, dd monthname ?yy? and day,
                     dd monthname 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 plat-
                     forms can represent the years 38-70,  so  an
                     error may result if these years are used.

              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 fol-
              lowing 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.

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


KEYWORDS
       clock, date, time
