Add a Time field to the WordPress Customizer. Includes sanitize function that formats the time as ('H:i')

WP Customizer - Time

$wp_customize->add_setting( 'themeslug_time_setting_id', array(
  'capability' => 'edit_theme_options',
  'sanitize_callback' => '',
  'default' => 1,
) );

$wp_customize->add_control( 'themeslug_time_setting_id', array(
  'type' => 'time',
  'section' => 'custom_section', // Add a default or your own section
  'label' => __( 'Custom Time' ),
  'description' => __( 'This is a custom time.' ),
) );

function themeslug_sanitize_time( $input ) {
  $time = new DateTime( $input );
  return $time->format('H:i');
}