Iowa Code § 7C.9: Nonbusiness days.

If the expiration date of either the one-hundred-twenty-day period or the thirty-day extension period described in subsection 1 or 2 of section 7C.7 is a Saturday, Sunday, or any day on which the offices of the state or banking institutions in the state are authorized or required to close, the expiration date is extended to the first day thereafter which is not a Saturday, Sunday, or other previously described day.