how to convert timestamp to date in mongodb?

Question

i am working on aggregation of mongodb collection.my mongodb collection has creation_time in timestamp.How will i can collect same day result and aggregate with next day res

Answer 1

In my case , I used

db.collection.aggregate([
  { "$project": {
    "date": { "$toDate": { 
        $multiply:["$_id",1000 ]
             } 
       }
  }}
])

convert timestamp from milliseconds to seconds.

Answer 2

You can use $toDate aggregation to convert timestamp to ISO date and $toLong to convert string timestamp to integer value in mongodb 3.6

db.collection.aggregate([
  { "$project": {
    "_id": {
      "$toDate": {
        "$toLong": "$_id"
      }
    }
  }},
  { "$group": {
    "_id": { "$dateToString": { "format": "%Y-%m-%d", "date": "$_id" } },
    "count": { "$sum": 1 }
  }}
])

Try it here

And with the previous versions

db.collection.aggregate([
  { "$project": {
    "date": { "$add": [ new Date(0), "$_id" ] }
  }}
])