Aggregation second solution

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