docs = [
	{
		"t" : ISODate("1969-12-31T23:59:59.999Z"),
		"m" : {
	
		},
		"_id" : 0
	}
]

const coll = db.c;
assert.commandWorked(db.createCollection(coll.getName(), {
timeseries: {timeField: 't', metaField: 'm'},
}));

assert.commandWorked(coll.insert(docs))

jsTestLog(db.system.buckets.c.find().toArray())

query = [
	{
		"$group" : {
			"_id" : "$t",
			"m" : {
				"$max" : "$t"
			}
		}
	}
]
jsTestLog(coll.aggregate(query).toArray())
// "m" contains the wrong result (rounded)