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In this chapter, we introduce how the Perl language handles dates and times.

Perl has the following functions for handling time:

• 1. time() function: Returns the number of seconds elapsed since January 1, 1970.
• 2. localtime() function: Gets the local timezone time.
• 3. gmtime() function: Gets Greenwich Mean Time (GMT).

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Current Time and Date

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

The following 9 symbols represent different date and time parameters:

sec, # Seconds, 0 to 61
min, # Minutes, 0 to 59
hour, # Hours, 0 to 24
mday, # Day of the month, 1 to 31
mon, # Month, 0 to 11
year, # Year, since 1900
wday, # Day of the week, 0-6, where 0 represents Sunday
yday, # Day of the year, 0-364, 365
isdst # True if Daylight Saving Time is in effect

An example is shown below:

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 output of the above example is:

12 June Sunday

If you call localtime() directly, it returns the time set in the system's current timezone. An example is as follows:

Example

#!/usr/bin/perl
$datestring = localtime();
print "Time and date: $datestringn";

The output of the above example is:

Time and date: Sun Jun 12 11:27:31 2016

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Greenwich Mean Time (GMT)

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

Example

#!/usr/bin/perl
$local_datestring = localtime();
print "Local time and date: $local_datestringn";
$gmt_datestring = gmtime();
print "GMT time and date: $gmt_datestringn";

The output of the above example is:

Local time and date: Sun Jun 12 11:32:14 2016
GMT time and date: Sun Jun 12 03:32:14 2016

From the example, we can see that the time in China is 8 hours ahead of Greenwich Mean Time.

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Formatting Date and Time

We can use the 9 time elements from the localtime() function to output time in a specified format. 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:SSn");
printf("%02d:%02d:%02d", $hour, $min, $sec);

The output of the above example is:

Formatted time: HH:MM:SS
11:35:23

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Epoch Time

We can use the time() function to get the Epoch time, which returns the number of seconds elapsed since January 1, 1970. An example is as follows:

Example

#!/usr/bin/perl
$epoc = time();
print "Seconds elapsed since January 1, 1970: $epocn";

The output of the above example is:

Seconds elapsed since January 1, 1970: 1465702883

We can output the time in a desired format:

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 = $epoc - 24 * 60 * 60;
($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 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

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POSIX Function strftime()

The strftime() function can format time into our desired format.

The following table lists some formatting symbols. The * indicates that the symbol depends on the local time:

Symbol	Description	Example
%a	Abbreviated weekday name (Sun..Sat) *	Thu
%A	Full weekday name (Sunday..Saturday) *	Thursday
%b	Abbreviated month name (Jan..Dec) *	Aug
%B	Full month name (January..December) *	August
%c	Date and time *	Thu Aug 23 14:55:02 2001
%C	Century divided by 100 and truncated to integer (00-99)	20
%d	Day of the month, zero-padded (01-31)	23
%D	Date format MM/DD/YY, equivalent to %m/%d/%y	08/23/01
%e	Day of the month, space-padded (1-31)	23
%F	ISO 8601 date format YYYY-MM-DD, similar to %Y-%m-%d	2001-08-23
%g	Two-digit year of the ISO 8601 week-based year (00-99)	01
%G	ISO 8601 week-based year	2001
%h	Abbreviated month name * (same as %b)	Aug
%H	Hour in 24-hour format (00-23)	14
%I	Hour in 12-hour format (01-12)	02
%j	Day of the year (001-366)	235
%m	Month as a decimal number (01-12)	08
%M	Minute (00-59)	55
%n	Newline character ('n')
%p	AM or PM designation	PM
%r	12-hour clock time (hh:mm:ss AM/PM) *	02:55:02 pm
%R	24-hour time format HH:MM, equivalent to %H:%M	14:55
%S	Second (00-61)	02
%t	Horizontal tab character ('t')
%T	24-hour time format (hh:mm:ss), equivalent to %H:%M:%S	14:55
%u	ISO 8601 weekday number (1-7, where Monday is 1)	4
%U	Week number of the year (Sunday as the first day of the week) (00-53)	33
%V	ISO 8601 week number (00-53)	34
%w	Day of the week (0-6, where Sunday is 0)	4
%W	Week number of the year (Monday as the first day of the week) (00-53)	34
%x	Date representation *	08/23/01
%X	Time representation *	14:55:02
%y	Year without century (00-99)	01
%Y	Year with century	2001
%z	ISO 8601 UTC offset from UTC (+hhmm or -hhmm)	+100
%Z	Timezone name or abbreviation *	CDT
%%	The literal % character	%

Example

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

The output of the above example is:

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