Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{"key":"2002-05-21T10:59:49.966Z"},{"key":"2003-05-21T10:59:49.966Z"}]
Query
db.collection.aggregate([{$project:{date:{$year:{$dateFromString:{dateString:"$key"}}}}}])
Result