clock(n)						       Tcl Built-In Commands							  clock(n)

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NAME

       clock - Obtain and manipulate time

SYNOPSIS

       clock option ?arg arg ...?
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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 integer 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 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 (00 - 52), Sunday is the first day of the week.

	      %w     Weekday number (Sunday = 0).

	      %W     Week of year (00 - 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 Windows):

	      %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 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 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 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 specific 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 acceptable formats are mm/dd?/yy?, monthname dd ?, yy?, dd monthname ?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 CCyymmddThhmmss, where T is the literal  T,  CCyymmdd  hhmmss,  or  CCyymmd-
		     dThh:mm:ss.

	      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 relative time is specified in units of days or more, ie, days, weeks,
	      fortnights, months or years.  This means that when crossing 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.

KEYWORDS

       clock, date, time

Tcl									8.3								  clock(n)