[{"name":"Taylor Scott","email":"taylor_scott@fakegmail.com","date":{"$date":"1970-11-15T05:54:02Z"}},{"name":"Jaqen H'ghar","email":"tom_wlaschiha@gameofthron.es","date":{"$date":"1981-11-08T04:32:25Z"}},{"name":"Yara Greyjoy","email":"gemma_whelan@gameofthron.es","date":{"$date":"2012-11-26T11:00:57Z"}}]

db.collection.aggregate([{$set:{date:{$toString:"$date"}}}])