In 2015, Ascension Day falls on May 14.
The Feast of the Ascension is always on a Thursday — 40 days after Easter — and ten days before Pentecost Sunday.
The Sunday between the two is known as Exaudi Sunday, particularly in Lutheran denominations. My 2013 post cites a beautiful sermon from my cyberfriend Dr Gregory Jackson of Ichabod which explains more.
GJ - ChurchMouse has more material than I can mention, so I am happy to have his blog updates linked in the left column.