Linux Manual Pages

Free Software * Books

Source Code

Free Media

Linux

Time::Piece

NAME
SYNOPSIS
DESCRIPTION
USAGE
CAVEATS
AUTHOR
License
SEE ALSO
BUGS

NAME

Time::Piece − Object Oriented time objects

SYNOPSIS

    use Time::Piece;
    my $t = localtime;
    print "Time is $t\n";
    print "Year is ", $t−>year, "\n";

DESCRIPTION

This module replaces the standard localtime and gmtime functions with implementations that return objects. It does so in a backwards compatible manner, so that using localtime/gmtime in the way documented in perlfunc will still return what you expect.

The module actually implements most of an interface described by Larry Wall on the perl5−porters mailing list here: http://www.xray.mpe.mpg.de/mailing−lists/perl5−porters/2000−01/msg00241.html

USAGE

After importing this module, when you use localtime or gmtime in a scalar context, rather than getting an ordinary scalar string representing the date and time, you get a Time::Piece object, whose stringification happens to produce the same effect as the localtime and gmtime functions. There is also a new() constructor provided, which is the same as localtime(), except when passed a Time::Piece object, in which case it’s a copy constructor. The following methods are available on the object:

    $t−>sec                 # also available as $t−>second
    $t−>min                 # also available as $t−>minute
    $t−>hour                # 24 hour
    $t−>mday                # also available as $t−>day_of_month
    $t−>mon                 # 1 = January
    $t−>_mon                # 0 = January
    $t−>monname             # Feb
    $t−>month               # same as $t−>monname
    $t−>fullmonth           # February
    $t−>year                # based at 0 (year 0 AD is, of course 1 BC)
    $t−>_year               # year minus 1900
    $t−>yy                  # 2 digit year
    $t−>wday                # 1 = Sunday
    $t−>_wday               # 0 = Sunday
    $t−>day_of_week         # 0 = Sunday
    $t−>wdayname            # Tue
    $t−>day                 # same as wdayname
    $t−>fullday             # Tuesday
    $t−>yday                # also available as $t−>day_of_year, 0 = Jan 01
    $t−>isdst               # also available as $t−>daylight_savings
    $t−>hms                 # 12:34:56
    $t−>hms(".")            # 12.34.56
    $t−>time                # same as $t−>hms
    $t−>ymd                 # 2000−02−29
    $t−>date                # same as $t−>ymd
    $t−>mdy                 # 02−29−2000
    $t−>mdy("/")            # 02/29/2000
    $t−>dmy                 # 29−02−2000
    $t−>dmy(".")            # 29.02.2000
    $t−>datetime            # 2000−02−29T12:34:56 (ISO 8601)
    $t−>cdate               # Tue Feb 29 12:34:56 2000
    "$t"                    # same as $t−>cdate
    $t−>epoch               # seconds since the epoch
    $t−>tzoffset            # timezone offset in a Time::Seconds object
    $t−>julian_day          # number of days since Julian period began
    $t−>mjd                 # modified Julian date (JD−2400000.5 days)
    $t−>week                # week number (ISO 8601)
    $t−>is_leap_year        # true if it its
    $t−>month_last_day      # 28−31
    $t−>time_separator($s)  # set the default separator (default ":")
    $t−>date_separator($s)  # set the default separator (default "−")
    $t−>day_list(@days)     # set the default weekdays
    $t−>mon_list(@days)     # set the default months
    $t−>strftime(FORMAT)    # same as POSIX::strftime (without the overhead
                            # of the full POSIX extension)
    $t−>strftime()          # "Tue, 29 Feb 2000 12:34:56 GMT"
    Time::Piece−>strptime(STRING, FORMAT)
                            # see strptime man page. Creates a new
                            # Time::Piece object

Local Locales
Both wdayname (day) and monname (month) allow passing in a list to use to index the name of the days against. This can be useful if you need to implement some form of localisation without actually installing or using locales.

my @days = qw( Dimanche Lundi Merdi Mercredi Jeudi Vendredi Samedi );
my $french_day = localtime−>day(@days);

These settings can be overriden globally too:

Time::Piece::day_list(@days);

Or for months:

Time::Piece::mon_list(@months);

And locally for months:

print localtime−>month(@months);

Date Calculations
It’s possible to use simple addition and subtraction of objects:

    use Time::Seconds;
    my $seconds = $t1 − $t2;
    $t1 += ONE_DAY; # add 1 day (constant from Time::Seconds)

The following are valid ($t1 and $t2 are Time::Piece objects):

    $t1 − $t2; # returns Time::Seconds object
    $t1 − 42; # returns Time::Piece object
    $t1 + 533; # returns Time::Piece object

However adding a Time::Piece object to another Time::Piece object will cause a runtime error.

Note that the first of the above returns a Time::Seconds object, so while examining the object will print the number of seconds (because of the overloading), you can also get the number of minutes, hours, days, weeks and years in that delta, using the Time::Seconds API .

In addition to adding seconds, there are two APIs for adding months and years:

$t−>add_months(6);
$t−>add_years(5);

The months and years can be negative for subtractions. Note that there is some "strange" behaviour when adding and subtracting months at the ends of months. Generally when the resulting month is shorter than the starting month then the number of overlap days is added. For example subtracting a month from 2008−03−31 will not result in 2008−02−31 as this is an impossible date. Instead you will get 2008−03−02. This appears to be consistent with other date manipulation tools.

Date Comparisons
Date comparisons are also possible, using the full suite of "<", ">", "<=", ">=", "<=>", "==" and "!=".

Date Parsing
Time::Piece has a built-in strptime() function (from FreeBSD), allowing you incredibly flexible date parsing routines. For example:

  my $t = Time::Piece−>strptime("Sunday 3rd Nov, 1943",
                                "%A %drd %b, %Y");
  print $t−>strftime("%a, %d %b %Y");

Outputs:

Wed, 03 Nov 1943

(see, it’s even smart enough to fix my obvious date bug)

For more information see "man strptime", which should be on all unix systems.

Alternatively look here: http://www.unix.com/man−page/FreeBSD/3/strftime/

YYYY−MM−DDThh:mm:ss
The ISO 8601 standard defines the date format to be YYYY-MM-DD, and the time format to be hh:mm:ss (24 hour clock), and if combined, they should be concatenated with date first and with a capital ’T’ in front of the time.

Week Number
The week number may be an unknown concept to some readers. The ISO 8601 standard defines that weeks begin on a Monday and week 1 of the year is the week that includes both January 4th and the first Thursday of the year. In other words, if the first Monday of January is the 2nd, 3rd, or 4th, the preceding days of the January are part of the last week of the preceding year. Week numbers range from 1 to 53.

Global Overriding
Finally, it’s possible to override localtime and gmtime everywhere, by including the ’:override’ tag in the import list:

use Time::Piece ':override';

CAVEATS

Setting $ENV{ TZ } in Threads on Win32
Note that when using perl in the default build configuration on Win32 (specifically, when perl is built with PERL_IMPLICIT_SYS ), each perl interpreter maintains its own copy of the environment and only the main interpreter will update the process environment seen by strftime.

Therefore, if you make changes to $ENV{ TZ } from inside a thread other than the main thread then those changes will not be seen by strftime if you subsequently call that with the %Z formatting code. You must change $ENV{ TZ } in the main thread to have the desired effect in this case (and you must also call _tzset() in the main thread to register the environment change).

Furthermore, remember that this caveat also applies to fork(), which is emulated by threads on Win32.

Use of epoch seconds
This module internally uses the epoch seconds system that is provided via the perl "time()" function and supported by "gmtime()" and "localtime()".

If your perl does not support times larger than "2^31" seconds then this module is likely to fail at processing dates beyond the year 2038. There are moves afoot to fix that in perl. Alternatively use 64 bit perl. Or if none of those are options, use the DateTime module which has support for years well into the future and past.

AUTHOR

Matt Sergeant, matt@sergeant.org Jarkko Hietaniemi, jhi@iki.fi (while creating Time::Piece for core perl)

License

This module is free software, you may distribute it under the same terms as Perl.

BUGS

The test harness leaves much to be desired. Patches welcome.

Opportunity

Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.

Education

Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.