I come from Relational Database background and we have a way to populate timestamp for row creation and update. I am having difficulty finding similar feature for DynamoDB.
There is no such functionality like DEFAULT CURRENT TIMESTAMP or UPDATE CURRENT_TIMESTAMP. You will have to set the date by yourself.
DEFAULT CURRENT TIMESTAMP
UPDATE CURRENT_TIMESTAMP
However if you want to keep track of changes on updates then you can use something like atomic counters.
Thus on every update your will increment the counter value.