time12h.js 221 Bytes
$.validator.addMethod( "time12h", function( value, element ) {
	return this.optional( element ) || /^((0?[1-9]|1[012])(:[0-5]\d){1,2}(\ ?[AP]M))$/i.test( value );
}, "Please enter a valid time in 12-hour am/pm format" );