Database
[{"id":11,"startDate":"07/04/2012",},{"id":11,"startDate":"07/04/2013",},{"id":11,"startDate":"07/04/2010",},{"id":11,"startDate":"07/04/2016",}]
Query
db.collection.aggregate([{"$set":{"startDate":{"$dateFromString":{"dateString":"$startDate","format":"%d/%m/%Y"}}}},{"$match":{"startDate":{"$gte":ISODate("2014-01-01T15:00:00.000Z")}}}])