You need to grab the WordPress date option on the first parameter of date_i18n function :
date_i18n( get_option( 'date_format' ), strtotime( '11/15-1976' ) );
You can see this example in the function codex page : date_i18n()
You need to grab the WordPress date option on the first parameter of date_i18n function :
date_i18n( get_option( 'date_format' ), strtotime( '11/15-1976' ) );
You can see this example in the function codex page : date_i18n()