Online PHP editor | refs for kboC7

<?php $calendar = [ 'p1' => [ ['start' => '2016-04-30 12:00', 'end' => '2016-05-01 03:00'] ], 'p2' => [ ['start' => '2016-04-30 03:00', 'end' => '2016-05-01 03:00'] ], 'p3' => [ ['start' => '2016-04-30 03:00', 'end' => '2016-04-30 13:31'], ['start' => '2016-04-30 15:26', 'end' => '2016-05-01 03:00'] ] ]; $tz = new DateTimeZone( date_default_timezone_get() ); $flat = call_user_func_array( 'array_merge', $calendar ); $min = date_create( min( array_column( $flat, 'start' ) ) )->getTimestamp()/60; $max = date_create( max( array_column( $flat, 'end' ) ) )->getTimestamp()/60; $free = gmp_sub( gmp_pow( 2, $max-$min ), gmp_pow( 2, 0 ) ); foreach( $calendar as $p ) { $pf = gmp_init( 0 ); foreach( $p as $time ) { $start = date_create( $time['start'] )->getTimestamp()/60; $end = date_create( $time['end'] )->getTimestamp()/60; $pf = gmp_or( $pf, gmp_sub( gmp_pow( 2, $end-$min ), gmp_pow( 2, $start-$min ) ) ); } $free = gmp_and( $free, $pf ); } $result = []; $start = $end = 0; while( ($start = gmp_scan1( $free, $end )) >= 0 ) { $end = gmp_scan0( $free, $start ); if( $end === False) $end = strlen( gmp_strval( $free, 2 ) )-1; $result[] = [ 'start' => date_create( '@'.($start+$min)*60 )->setTimezone( $tz )->format( 'Y-m-d H:i:s' ), 'end' => date_create( '@'.($end+$min)*60 )->setTimezone( $tz )->format( 'Y-m-d H:i:s' ) ]; } print_r( $result );