Mongoose: moment().format not working - node.js

Question

Im having Mongoose schema as follows:
createdOn: {
type: String,
//default: Date.now,
default: moment(new Date(Date.now())).format('MMM Do YY') //npm install moment --save # npm
},
updatedOn: {
type: String,
//default: Date.now
default: moment(new Date(Date.now())).format('MMM Do YY')
}
UPDATE:
After changing the type to String,
I get :
Fri Jul 28 2017 14:43:40 GMT+0530 (IST)
How to remove the time and SMT.
I need to keep only Fri Jul 28 2017
I installed Moment package of node js (http://momentjs.com/)
Whats wrong in my schema above:
I get
MongooseError: Cast to date failed for value "Aug 7th 17" at path "updatedOn"
message: 'Cast to date failed for value "Aug 7th 17" at path "updatedOn"',
name: 'CastError',
stringValue: '"Aug 7th 17"',
kind: 'date',
value: 'Aug 7th 17',
path: 'updatedOn',
reason: undefined }

Answer 1

The double default assignment looks wrong.
default: default: moment(new Date(Date.now())).format('MMM Do YY')
As a better practice, you should consider just using UNIX timestamps rather than formatted date strings. Timestamps will allow you to easily track statistics on the database.
So you could just use the:
Date.now() // returns a UNIX timestamp
In moment.js a UNIX timestamp:
moment().unix()
If for some reason you need the timestamp in a string format you could always just do:
moment().unix() + ''