foo:PRIMARY> db.createCollection("coll", {timeseries: {timeField: 'time'}}) { "ok" : 1, "$clusterTime" : { "clusterTime" : Timestamp(1691419064, 2), "signature" : { "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) } }, "operationTime" : Timestamp(1691419064, 2) } foo:PRIMARY> db.runCommand({insert: "coll", documents: [{x: 0, time: ISODate()}, {x: 1}], ordered: true}) { "n" : 2, "electionId" : ObjectId("7fffffff0000000000000004"), "opTime" : { "ts" : Timestamp(1691419106, 1), "t" : NumberLong(4) }, "writeErrors" : [ { "index" : 1, "code" : 2, "errmsg" : "'time' must be present and contain a valid BSON UTC datetime value" } ], "ok" : 1, "$clusterTime" : { "clusterTime" : Timestamp(1691419106, 1), "signature" : { "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) } }, "operationTime" : Timestamp(1691419106, 1) } foo:PRIMARY> db.runCommand({insert: "coll", documents: [{x: 0, time: ISODate()}, {x: 1}], ordered: false}) { "n" : 1, "electionId" : ObjectId("7fffffff0000000000000004"), "opTime" : { "ts" : Timestamp(1691419125, 1), "t" : NumberLong(4) }, "writeErrors" : [ { "index" : 1, "code" : 2, "errmsg" : "'time' must be present and contain a valid BSON UTC datetime value" } ], "ok" : 1, "$clusterTime" : { "clusterTime" : Timestamp(1691419125, 1), "signature" : { "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) } }, "operationTime" : Timestamp(1691419125, 1) }