my $workbook = Excel::Writer::XLSX->new( 'build_results.xlsx' ); my $worksheet = $workbook->add_worksheet(); my $format = $workbook->add_format( num_format => '[hh]:mm:ss' ); $worksheet->write_date_time( "A$col", '12:20:12', $format ); # i need this to be considered 12 hours 20 mins and 12 secs.