[{"_id":ObjectId("5e7331614dd99d1a30143a58"),"status":"rejected","from":ISODate("2020-03-17T08:46:02.552Z"),"to":ISODate("2020-03-18T08:46:07.124Z")},{"_id":ObjectId("5e7331614dd99d1a30143a59"),"status":"rejected","from":ISODate("2020-03-02T08:08:32.819Z"),"to":ISODate("2020-03-05T08:08:37.125Z"),},{"_id":ObjectId("5e7331614dd99d1a30143a60"),"status":"approved","from":ISODate("2020-03-17T08:46:02.552Z"),"to":ISODate("2020-03-18T08:46:07.124Z")},{"_id":ObjectId("5e7331614dd99d1a30143a61"),"status":"pending","from":ISODate("2020-03-02T08:08:32.819Z"),"to":ISODate("2020-03-05T08:08:37.125Z"),},{"_id":ObjectId("5e7331614dd99d1a30143a62"),"status":"rejected","from":ISODate("2020-03-02T08:08:32.819Z"),"to":ISODate("2020-04-02T08:08:37.125Z"),},{"_id":ObjectId("5e7331614dd99d1a30143a63"),"status":"rejected","from":ISODate("2019-03-02T08:08:32.819Z"),"to":ISODate("2020-04-02T08:08:37.125Z"),}]

db.collection.aggregate([{$match:{status:"rejected"}},{$addFields:{daysCount:{$round:{$divide:[{$subtract:["$to","$from"]},86400000]}}}}])