{ "_id" : ObjectId("525847b17bb5149dea3bb079"), "n" : 5 } > db.foo.update({ n : 5 }, {$currentDate: {date : false }}) { "_id" : ObjectId("525847b17bb5149dea3bb079"), "n" : 5, "date" : ISODate("2013-10-15T17:35:11.465Z") }
Behavior is not intuitive as I expect date field not to be set in this case.