Perl Time and Date

This section introduces how Perl handles time and date.

There are several functions in Perl for time manipulation:

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

Current Time and Date

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

The following 9 symbols represent different time and date parameters:

sec,     # Seconds, 0 to 61
min,     # Minutes, 0 to 59
hour,    # Hours, 0 to 24
mday,    # Day, 1 to 31
mon,     # Month, 0 to 11
year,    # Year, starting from 1900
wday,    # Day of the week, 0-6, 0 being Sunday
yday,    # Day of the year, 0-364, 365
isdst    # True if daylight saving time is in effect

Here is an example:

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 in the system's current timezone, as shown in the following example:

Example

#!/usr/bin/perl

$datestring = localtime();
print "The time and date is: $datestring\n";

The output of the above example is:

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

Greenwich Mean Time (GMT)

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

Example

#!/usr/bin/perl

$local_datestring = localtime();
print "Local time and date is: $local_datestring\n";

$gmt_datestring = gmtime();
print "GMT time and date is: $gmt_datestring\n";

The output of the above example is:

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

Formatting Date and Time

We can use the 9 time elements from the localtime() function to output the time in the desired format. Formatting is done using 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 output of the above example is:

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

Epoch Time

We can use the time() function to get the epoch time, which returns the number of seconds since January 1, 1970. Here is an example:

Example

#!/usr/bin/perl

$epoc = time();

print "The number of seconds since January 1, 1970 is: $epoc\n";

The output of the above example is:

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

We can also 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 for one day ago

The output of the above example is:

Current time and date: 2023-6-12 11:35:23

($sec, $min, $hour, $mday, $mon, $year, $wday, $yday, $isdst) = localtime($epoc);
print "Yesterday's date and time: ";
printf("%d-%d-%d %d:%d:%d", $year + 1900, $mon + 1, $mday, $hour, $min, $sec);

print "\n";

Example output:

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

POSIX Function strftime()

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

The following table lists some formatting symbols, with an asterisk (*) indicating that the format is dependent on the local time:

Example

#!/usr/bin/perl
use POSIX qw(strftime);

$datestring = strftime "%Y-%m-%d %H:%M:%S", localtime;
printf("Date and Time - $datestring\n");

# GMT formatted date and time
$datestring = strftime "%Y-%m-%d %H:%M:%S", gmtime;
printf("Date and Time - $datestring\n");

Output:

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