Mother’s Day [Not a public holiday] Calendar When: May 9, 2010 all-day 2010-05-09T00:00:00-05:00 2010-05-10T00:00:00-05:00 Where: USA Holiday 2nd Sunday in May. Not a public holiday.. Not a public holiday, but a legal national holiday observed on the second Sunday in May in the United States Information provided by www.officeholidays.com