sub parseWebdate {
    my ($str) = @_;

    if($str =~ /^([+-])(\d+)(\w)/) {
        my %multipliers = (
            s   => 1,
            m   => 60,
            h   => 60*60,
            d   => 60*60*24,
            W   => 60*60*24*7,
            M   => 60*60*24*30,
            y   => 60*60*24*365,
        );
        my ($direction, $amount, $multiplier) = ($1, $2, $3);
        if(!defined($multipliers{$multiplier})) {
            croak("Undefined delta time multiplier $multiplier");
        }
        if($direction eq '-') {
            $amount = $amount * -1;
        }
        return time() + ($amount * $multipliers{$multiplier});
    }

    # normal time string
    return str2time($str);
}