Perl date and time

In this chapter, we introduce to you the processing of time and date in Perl language.

There are several functions for processing time in Perl:

1. time() function: returns the accumulated number of seconds since January 1, 1970

2. localtime() function: get the local time zone time

3. gmtime() function: Get Greenwich Mean Time

Current time and date

Next let's look at the localtime() function, which returns the current time and date without arguments.

The following 9 symbols represent different time and date parameters:

 sec, # seconds, 0 to 61min, # minutes, 0 to 59hour, # hours, 0 to 24mday, # days, 1 to 31mon, # months, 0 to 11year, # years, starting from 1900 wday, # day of the week, 0 -6,0 means Sunday yday, # The day of the year, 0-364,365isdst # True if daylight saving time is in effect

Example demonstration is as follows:

Example

#!/usr/bin/perl @months = qw( January, February, March, April, May, June, July, August, September, October, November, December ) ; @days = qw( Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday ) ; ( $ sec , $min , $hour , $mday , $mon , $year , $wday , $yday , $isdst ) = localtime ( ) ; print " $mday $months [ $mon ] $days [ $wday ] n " ;

The execution output of the above example is:

 Sunday 12 June

If localtime() is called directly, it returns the time of the system's current time zone setting. The example is as follows:

Example

#!/usr/bin/perl $datestring = localtime ( ) ; print " The time and date are: $datestring n " ;

The execution output of the above example is:

 The date and time is: Sun Jun 12 11:27:31 2016

Greenwich Mean Time (GMT)

The function gmtime() is similar to localtime(), but it returns standard Greenwich Time.

Example

#!/usr/bin/perl $local_datestring = localtime ( ) ; print " The local time and date is: $local_datestring n " ; $gmt_datestring = gmtime ( ) ; print " The GMT time and date is: $gmt_datestring n " ;

The execution output of the above example is:

 The local time and date is: Sun Jun 12 11:32:14 2016GMT The time and date is: Sun Jun 12 03:32:14 2016

We can see from the example that the time in China is 8 hours different from Greenwich Mean Time.

Format date and time

We can use the 9 time elements of the localtime() function to output the format time that needs to be formulated. Formatted output uses the printf() function:

Example

#!/usr/bin/perl ( $sec , $min , $hour , $mday , $mon , $year , $wday , $yday , $isdst ) = localtime ( ) ; printf ( " Formatted time: HH:MM:SS n " ) ; printf ( " %02d:%02d:%02d " , $hour , $min , $sec ) ;

The execution output of the above example is:

 Formatting time: HH:MM:SS11:35:23

Epoch Time

We can get the epoch time using the time() function, which returns the number of seconds since January 1, 1970. Examples are as follows:

Example

#!/usr/bin/perl $epoc = time ( ) ; print " The accumulated number of seconds since January 1, 1970 is: $epoc n " ;

The execution output of the above example is:

 The number of seconds accumulated since January 1, 1970 is: 1465702883

We can output a time format we want:

Example

#!/usr/bin/perl ( $sec , $min , $hour , $mday , $mon , $year , $wday , $yday , $isdst ) = localtime ( ) ; print " Current time and date: " ; printf ( " %d-%d-%d %d:%d:%d " , $year + 1900 , $mon + 1 , $mday , $hour , $min , $sec ) ; print " n " ; $epoc = time ( ) ; $epoc = $epoc - 24 * 60 * 60 ; # seconds of time one day ago ( $sec , $min , $hour , $mday , $mon , $year , $wday , $yday , $isdst ) = localtime ( $epoc ) ; print " Yesterday's time and date: " ; printf ( " %d-%d-%d %d:%d:%d " , $year + 1900 , $mon + 1 , $mday , $hour , $min , $sec ) ; print " n " ;

The execution output of the above example is:

 Current time and date: 2017-3-15 12:47:54 Yesterday’s time and date: 2017-3-14 12:47:54

POSIX function strftime()

The function strftime() can format the time into the format we want.

The following table lists some formatting symbols. The * symbol indicates that you want to rely on local time:

symbol	describe	Example
%a	Abbreviation of day of the week (Sun..Sat) *	Thu
%A	The full name of the day of the week (Sunday..Saturday) *	Thursday
%b	Abbreviation of month (Jan..Dec) *	Aug
%B	The full name of the month (January..December) *	August
%c	Date and time*	Thu Aug 23 14:55:02 2001
%C	The year is divided by 100 and rounded ( 00-99 )	20
%d	The day of the month ( 01-31 )	23
%D	Date, MM/DD/YY is equal to %m/%d/%y	08/23/01
%e	The day of the month, using spaces to fill single digits ( 1-31 )	23
%F	The abbreviation of YYYY-MM-DD is similar to %Y-%m-%d	2001-08-23
%g	Last two digits of year ( 00-99 )	01
%g	Year	2001
%h	Month abbreviation* (same as %b option)	Aug
%H	24-hour format ( 00-23 )	14
%I	12-hour format ( 01-12 )	02
%j	Day of the year ( 001-366 )	235
%m	Month( 01-12 )	08
%M	Minutes ( 00-59 )	55
%n	new line ( 'n' )
%p	Show AM or PM	PM
%r	Time (hh:mm:ss AM or PM), 12 hours*	02:55:02 pm
%R	24-hour HH:MM time format, equivalent to %H:%M	14:55
%S	Number of seconds ( 00-61 )	02
%t	Horizontal tab ( 't' )
%T	Time (24-hour format) (hh:mm:ss), equivalent to %H:%M:%S	14:55
%u	ISO 8601 day of the week format, Monday is 1 ( 1-7 )	4
%U	Week number of the year, Sunday is the first day ( 00-53 )	33
%V	ISO 8601 week ( 00-53 )	34
%w	Day of the week (0 represents Sunday) ( 0-6 )	4
%W	Week number of the year, Monday is the first day ( 00-53 )	34
%x	Date display format (mm/dd/yy) *	08/23/01
%X	Display time format*	14:55:02
%y	Year, two digits ( 00-99 )	01
%Y	Year	2001
%z	Time zone offset between ISO 8601 and UTC (1 minute=1, 1 hour=100)	+100
%Z	The name of the current time zone, such as "China Standard Time" *	CDT
%%	% symbol	%

Example

#!/usr/bin/perl use POSIX qw( strftime ) ; $datestring = strftime " %Y-%m-%d %H:%M:%S " , localtime ; printf ( " Time and date- $datestring n " ) ; # GMT formatted time and date $datestring = strftime " %Y-%m-%d %H:%M:%S " , gmtime ; printf ( " Time and date - $datestring n " ) ;

The execution output of the above example is:

 Time and date - 2016-06-12 12:15:13 Time and date - 2016-06-12 04:15:13