src/parse/recur.js
function (id, vals) {
      var custom = later.modifier[id];
      if(!custom) throw new Error('Custom modifier ' + id + ' not recognized!');

      modifier = id;
      values = arguments[1] instanceof Array ? arguments[1] : [arguments[1]];
      return this;
    }
function (id, vals) {
      var custom = later.modifier[id];
      if(!custom) throw new Error('Custom modifier ' + id + ' not recognized!');

      modifier = id;
      values = arguments[1] instanceof Array ? arguments[1] : [arguments[1]];
      return this;
    }
function ( id , vals ) { var custom = later . modifier [ id ] ; if ( ! custom ) throw new Error ( 'Custom modifier ' + id + ' not recognized!' ) ; modifier = id ; values = arguments [ 1 ] instanceof Array ? arguments [ 1 ] : [ arguments [ 1 ] ] ; return this ; }
Custom modifier.

recur().on(2011, 2012, 2013).custom('partOfDay');

@api public
Custom modifier .