Use DateTime: 
my $dt = DateTime::Format::ISO8601->new();
$dt->parse_datetime( $date_string );
print( $dt->is_dst ? 'Y' : 'N' )

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Update: fglock is right; use the syntax he shows in his reply to the OP.

In reply to Re: Daylight Savings Time Determination by simonm
in thread Daylight Savings Time Determination by rtremaine

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