Chopped Time

The downside to using localtime (or gmtime) in the scalar context is that it simply spits out a pre-formatted result. You may wish to return the individual values for month, day, year and so on, which you might, for example, format in an alternative manner of your own construction. When you call localtime from within a "list context" -- assigning its return values to an array -- you receive the time chopped and diced into bite sized pieces.

Calling localtime in a list context yields the following values in this exact order:

List items returned by the localtime (or gmtime) function.

List index	Description	Values	Notes
0	seconds	0-59
1	minutes	0-59
2	hour	0-23
3	day of the month	1-31
4	month	0-11	0=January, 11=December
5	year	minus 1900	The year value is not the last two digits of the year, it is the current year minus 1900; e.g., 105 would mean the year 2005 (1900+105). Perl is therefore Y2K compliant!
6	day of the week	0-6	0=Sunday, 6=Saturday
7	day of the year	0-364
8	daylight savings time flag	0 or 1	1 (True) if date falls during Daylight Savings Time, 0 (False) otherwise.

One way, then, to grab all the chopped bits of time is to assign localtime to a list of scalar variables:

($seconds,$minutes,$hour,
 $monthday,$month,$year,
 $weekday,$yearday,$dst_flag)=localtime(time);

The trouble with this approach is twofold: for one, Perl returns values such as the day of the week and the month as numeric values, not names, which is not exactly suitable for human display. Second, you may not be interested in all of these bits, so you may not want to create variables that you're never going to use in the script (such as $dst_flag).

A clever way to pick out, for example, the month and translate it immediately into its respective name, relies on nested list references. Watch closely:

$day=(Sunday,Monday,Tuesday,
      Wednesday,Thursday,Friday,Saturday)[(localtime(time))[

The above snippet revolves around an "anonymous array", a list of weekday names which is not assigned to a particular list variable. We specify a single element of that array, that element being "(localtime(time))[6]]". In turn, "(localtime(time))" itself returns the list of time variables seen in the earlier table, from which we specify the element at index 6, which is the day of the week. We can use the same trick to pluck the name of the month.

$month=(January,February,March,
      April,May,June,July,
      August,September,October,
      November,December)[(localtime(time))[4]];

Although both examples above rely on the current time, you can of course replace time with any epoch time you wish.

An alternative to using Perl's default localtime function (or gmtime) is to use the module Time::localtime, which is included in the standard Perl distribution. In fact, this module behaves in nearly the exact same way as localtime -- meaning that it converts epoch time into localized time -- but allows for a slightly easier way to pick out the bits and pieces.

use Time::localtime;
$tomorrow=time+86400;
$timeVar=localtime($tomorrow);
$day=(Sunday,Monday,Tuesday,
      Wednesday,Thursday,Friday,Saturday)[$timeVar->wday];
      

Notice in the above script that we assign localtime to a scalar variable -- you can then call methods from this variable which return relevant time information, such as the day of the week ($timeVar->wday). The data is still returned as a numeric value, so we continue to rely on the anonymous array trick to translate this value into the day name. The convenience is largely in the fact that you can call upon a single item of time data by name rather than needing to refer to list indices. Using the localtime object in this manner you can call the following methods. Each of these values has the same range and meaning as those returned by the localtime function as seen in the previous table.

Methods of the localtime object.

sec	Seconds
min	Minutes
hour	Hour
mday	Day of the month
mon	Month
year	Year
wday	Day of the week
yday	Day of the year
isdst	Daylight Savings Time Flag

Remember that the Time::localtime module adjusts time for your particular time zone. You can alternately use the Time::gmtime module as a replacement for the gmtime function if you wish to stick with GMT time.

Human Friendly Time
The Perl You Need to Know
Reversing Time