I am parsing dates and datetimes input by users who aren't too careful with their formatting. Date::Parse seems great because it handles most cases I need to handle.

Except datetimes between 1901-01-01 00:00:00 and 1968-12-31 23:59:59, as I found out today. For those datetimes, Date::Parse str2time adds an extra 100 years when it parses the datetime to epoch time.

Here is the code I am using to parse the datetimes:

#!/usr/bin/perl
#---------------------------------------------------------------------
# format_date.pl
#
# format variable date inputs
#---------------------------------------------------------------------

use strict;
use warnings;

use Date::Parse;
use DateTime;

my $DEFAULT_TIME_ZONE = "GMT";

my @dates = (
    "1899-06-24 09:44:00",
    "1900-12-31 23:59:59",
    "1901-01-01 00:00:00",
    "1960-12-31 23:59:59",
    "1966-06-24 09:44:00",
    "1968-12-31 23:59:59",
    "1969-01-01 00:00:00",
    "1969-12-31 23:59:59",
    "1970-01-01 00:00:01",
    "2000-01-01 00:00:00",
    "2017-06-24 23:59:59",
    "2018-06-24 09:44:00",
    "2238-06-24 09:44:00"

);

foreach my $string (@dates) {

    # format datetime field from any valid datetime input
    # default time zone is used if timezone is not included in string
    my $epoch = str2time( $string, $DEFAULT_TIME_ZONE );

    # error if date is not correctly parsed
    if ( !$epoch ) {
        die("ERROR ====> invalid datetime ($string), "
        . "datetime format should be YYYY-MM-DD HH:MM:SS");
    }

    my $date = DateTime->from_epoch( epoch => $epoch );

    printf( "formatting datetime: value = %20s, epoch = %20u, "
            . "date = %20s\n", $string, $epoch, $date );

}

exit 0;
[download]

Side note: I need to improve my error handling because the valid date 1970-01-01 00:00:00 will throw an error.

The additional 100 years for dates between 1901 and 1969 can be seen in the output:

formatting datetime: value =  1899-06-24 09:44:00, epoch = 18446744071
+484095456, date =  1899-06-24T09:44:00
formatting datetime: value =  1900-12-31 23:59:59, epoch = 18446744071
+532098815, date =  1900-12-31T23:59:59
formatting datetime: value =  1901-01-01 00:00:00, epoch =            
+978307200, date =  2001-01-01T00:00:00
formatting datetime: value =  1960-12-31 23:59:59, epoch =           2
+871763199, date =  2060-12-31T23:59:59
formatting datetime: value =  1966-06-24 09:44:00, epoch =           3
+044598240, date =  2066-06-24T09:44:00
formatting datetime: value =  1968-12-31 23:59:59, epoch =           3
+124223999, date =  2068-12-31T23:59:59
formatting datetime: value =  1969-01-01 00:00:00, epoch = 18446744073
+678015616, date =  1969-01-01T00:00:00
formatting datetime: value =  1969-12-31 23:59:59, epoch = 18446744073
+709551615, date =  1969-12-31T23:59:59
formatting datetime: value =  1970-01-01 00:00:01, epoch =            
+        1, date =  1970-01-01T00:00:01
formatting datetime: value =  2000-01-01 00:00:00, epoch =            
+946684800, date =  2000-01-01T00:00:00
formatting datetime: value =  2017-06-24 23:59:59, epoch =           1
+498348799, date =  2017-06-24T23:59:59
formatting datetime: value =  2018-06-24 09:44:00, epoch =           1
+529833440, date =  2018-06-24T09:44:00
formatting datetime: value =  2238-06-24 09:44:00, epoch =           8
+472332640, date =  2238-06-24T09:44:00
[download]

The Date::Parse documentation suggests it can handle dates at least as old at 1901-01-01. The Time::Local documentation suggest it should be able handle dates even older.

How should I handle this oddity? Is there a better way to parse variable input formats?