The most stringent enrollment requirement for any of the three federal educational tax benefits is the one for the American Opportunity Tax Credit, which requires that the student must be enrolled at least half time for at least one academic period beginning in the tax year.

If your school uses a calendar other than the semester, that is perfectly fine. However your school defines its calendar, your enrollment for one academic period meets the test.

For more information, please see IRS Education Benefits Comparison Chart.