[{"key":1,"dt":{"$date":"2021-04-17T07:00:04.863Z"}},{"key":2,"dt":{"$date":"2021-04-17T07:30:04.863Z"}},{"key":3,"dt":{"$date":"2021-04-17T08:00:04.863Z"}},{"key":4,"dt":{"$date":"2021-04-17T08:30:04.863Z"}},{"key":5,"dt":{"$date":"2021-04-17T09:30:04.863Z"}}]

db.collection.aggregate([{$match:{$expr:{$eq:[{$year:"$dt"},2021]},/** match year*/$or:[{$and:[/** match hour 7 and minutes 30+*/{$expr:{$eq:[{"$hour":"$dt"},7]}},{$expr:{$gte:[{"$minute":"$dt"},30]}}]},{$and:[/** match hour 8 and minutes less than 30*/{$expr:{$eq:[{"$hour":"$dt"},8]}},{$expr:{$lt:[{"$minute":"$dt"},30]}}]},]}}])