In Amazon DynamoDB, Date Time value will be stored as String.

When the record is created in Salesforce, DynamoDB will have the value in GMT/UTC. When the record is created in DynamoDB, make sure the value of the Date Time is in GMT/UTC.

Sample Value:

2022-12-01T14:00:00Z

Above Date Time is 1st December 2 PM GMT/UTC.

Salesforce External Object Date Time Field:

Salesforce External Object Record with Date Time Value: