[{"mac":"aa:bb:cc:dd:ee:ff","date":ISODate("2016-11-15")},{"mac":"aa:bb:cc:dd:ee:ff","date":ISODate("2016-11-19")},{"mac":"aa:bb:cc:dd:ee:ff","date":ISODate("2016-11-20")},{"mac":"aa:bb:cc:dd:ee:ff","date":ISODate("2016-11-19")},{"mac":"ff:ee:dd:cc:bb:aa","date":ISODate("2016-11-19")},{"mac":"ff:ee:dd:cc:bb:aa","date":ISODate("2016-11-26")}]

db.collection.aggregate([{"$sort":{"date":-1}},{"$group":{"_id":"$mac","date":{"$push":"$date"}}},{"$project":{"_id":"$mac","laps":{"$subtract":[{"$arrayElemAt":["$date",0]},{"$arrayElemAt":["$date",1]}]}}},{"$group":{"_id":null,"1_day":{"$sum":{"$cond":[{"$lte":["$laps",86400000]},1,0]}},"2_7days":{"$sum":{"$cond":[{"$and":[{"$gt":["$laps",172800000]},{"$lte":["$laps",604800000]},]},1,0]}}}}])