Time::Piece(3p) Perl Programmers Reference Guide Time::Piece(3p)

Time::Piece(3p) Perl Programmers Reference Guide Time::Piece(3p) #

Time::Piece(3p) Perl Programmers Reference Guide Time::Piece(3p)

NNAAMMEE #

 Time::Piece - Object Oriented time objects

SSYYNNOOPPSSIISS #

     use Time::Piece;

     my $t = localtime;
     print "Time is $t\n";
     print "Year is ", $t->year, "\n";

DDEESSCCRRIIPPTTIIOONN #

 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:
 <https://www.nntp.perl.org/group/perl.perl5.porters/2000/01/msg5283.html>

UUSSAAGGEE #

 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 nneeww(()) constructor provided, which is the same as
 llooccaallttiimmee(()), 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's a leap year
     $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

 Note that "localtime" and "gmtime" are not listed above.  If called as
 methods on a Time::Piece object, they act as constructors, returning a
 new Time::Piece object for the current time.  In other words: they're not
 useful as methods.

LLooccaall LLooccaalleess 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. Note that this is a global override and will affect all Time::Piece instances.

   my @days = qw( Dimanche Lundi Merdi Mercredi Jeudi Vendredi Samedi );

   my $french_day = localtime->day(@days);

 These settings can be overridden globally too:

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

 Or for months:

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

 And locally for months:

   print localtime->month(@months);

 Or to populate with your current system locale call:
     Time::Piece->uussee__llooccaallee(());

DDaattee CCaallccuullaattiioonnss 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 = $t->add_months(6);
     $t = $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.

TTrruunnccaattiioonn Calling the “truncate” method returns a copy of the object but with the time truncated to the start of the supplied unit.

     $t = $t->truncate(to => 'day');

 This example will set the time to midnight on the same date which $t had
 previously. Allowed values for the "to" parameter are: "year", "quarter",
 "month", "day", "hour", "minute" and "second".

DDaattee CCoommppaarriissoonnss Date comparisons are also possible, using the full suite of “<”, “>”, “<=”, “>=”, “<=>”, “==” and “!=”.

DDaattee PPaarrssiinngg Time::Piece has a built-in ssttrrppttiimmee(()) 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/>

 _C_A_V_E_A_T _%_A_, _%_a_, _%_B_, _%_b_, _a_n_d _f_r_i_e_n_d_s

 Time::Piece::strptime by default can only parse American English date
 names.  Meanwhile, Time::Piece->ssttrrffttiimmee(()) will return date names that
 use the current configured system locale. This means dates returned by
 strftime might not be able to be parsed by strptime. This is the default
 behavior and can be overridden by calling Time::Piece->uussee__llooccaallee(()). This
 builds a list of the current locale's day and month names which strptime
 will use to parse with.  Note this is a global override and will affect
 all Time::Piece instances.

 For instance with a German locale:

     localtime->day_list();

 Returns

     ( 'Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat' )

 While:

     Time::Piece->use_locale();
     localtime->day_list();

 Returns

     ( 'So', 'Mo', 'Di', 'Mi', 'Do', 'Fr', 'Sa' )

YYYYYYYY--MMMM--DDDDTThhhh::mmmm::ssss 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.

WWeeeekk NNuummbbeerr The _w_e_e_k _n_u_m_b_e_r 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.

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

     use Time::Piece ':override';

CCAAVVEEAATTSS #

SSeettttiinngg $$EENNVV{{TTZZ}} iinn TThhrreeaaddss oonn WWiinn3322 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 __ttzzsseett(()) in the main thread to register the
 environment change).

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

UUssee ooff eeppoocchh sseeccoonnddss 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.

 Also, the internal representation of Time::Piece->strftime deviates from
 the standard POSIX implementation in that is uses the epoch (instead of
 separate year, month, day parts). This change was added in version 1.30.
 If you must have a more traditional strftime (which will normally never
 calculate day light saving times correctly), you can pass the date parts
 from Time::Piece into the strftime function provided by the POSIX module
 (see strftime in POSIX ).

AAUUTTHHOORR #

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

CCOOPPYYRRIIGGHHTT AANNDD LLIICCEENNSSEE #

 Copyright 2001, Larry Wall.

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

SSEEEE AALLSSOO #

 The excellent Calendar FAQ at
 <http://www.tondering.dk/claus/calendar.html>

BBUUGGSS #

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

perl v5.36.3 2021-03-02 Time::Piece(3p)