sub convert_format
{
    my $format = shift;
    # If we have a 4 digit year
    $format =~ s/9999/YYYY/;
    # Two cases:
    if ($format =~ /^Y/) {
        # Month first
        $format =~ s/99/MM/;
        $format =~ s/99/DD/;
    }
    else {
        # Day first
        $format =~ s/99/DD/;
        $format =~ s/99/MM/;
    }
    # Handle two digit year
    $format =~ s/99/RR/;
    return $format;
}