USING MONGODB

I need to use the db.collection.updateMany() method on the inventory collection to update all documents where qty is less than 50.

My code is:

db.inventory.updateMany({ "qty": { $lt: 50 } },{$set: { "size.uom": "in", status: "P" }, "currentDate": { "lastModified": true }})

however, I keep getting this error:

MongoServerError: Unknown modifier: currentDate. Expected a valid update modifier or pipeline-style update specified as an array

Please help :)