Database
[{citizens:[{name:"John",birthday:ISODate("1993-07-13T00:00:00.000Z")},{name:"Sarah",birthday:ISODate("1996-07-13T00:00:00.000Z")},{name:"Natalia",birthday:ISODate("2015-07-13T00:00:00.000Z")}]},{citizens:[{name:"Leo",birthday:ISODate("1994-02-08T00:00:00.000Z")},{name:"Paul",birthday:ISODate("1934-09-13T00:00:00.000Z")},{name:"Rego",birthday:ISODate("2019-01-29T00:00:00.000Z")}]}]
Query
db.collection.update({},{$set:{"citizens.$[elem].status":"adult"},},{arrayFilters:[{"elem.birthday":{$lte:ISODate("2004-07-27T00:00:00.000Z")}}],multi:true,})