timestamps do not work on embedded documents or subdocuments in mongoose

normally timestamps would work

var UserSchema = Schema ({{
  name: String,
  description:String
},{
 timestamps: true
})

but timestapms does not work in

var UserSchema = Schema({

                name: String,
                description: String,
                publications: [{
                    title: String,
                    description: String
                }, {
                    timestamps: true
                }]
            })

I've been looking for hours and nothing that I can solve this