On successfully calling ScheduleKeyDeletion, the timestamp in the DeletionDate field returned from AWS is encoded in Scientific Notation/Standard Form. Local KMS returns the value as a standard integer.

For example:
AWS returns: 1.5565824E9
Local KMS returns: 1556582400

AWS' SDKs appear to transparently accept either correctly.

There appears no easy way to force Go to output the value as a number, in Scientific Notation. The community conscientious seems to be that as the interpreter should read both numbers identically, thus Go is working as expected.