What is extended active duty for the Earned Income Credit?

Extended active duty is military duty ordered for an indefinite period or for a period of time of more than 90 days. Once you begin serving extended active duty, you are considered to be on extended active duty even if you don't serve more than 90 days.

If you were on extended active duty outside the United States, your main home is considered to be in the United States during that period of duty.