Hail Which Festival Day?
Today the Church celebrates the Feast of the Ascension, when Christ ascended into Heaven forty days after He rose from the dead.
In most provinces of the USA, and in entire countries throughout the world, the Feast has been moved to the following Sunday. We could just leave well enough alone, and transfer the obligation itself to the Sunday within the octave of the Feast, but the Western church got rid of many of its octaves in the mid-1950s, and a few more since then. You'd have to explain to people what an octave is, and that is such a pain. So today will be remembered as just another Easter weekday.
But it doesn't matter, really. After all, most biblical scholars agree that Jesus ascended into Heaven forty-three days after He rose from the dead, not forty days as previously believed. The number of forty was arrived at by the end of the third century, to make it easier for Christians to count the days after Easter on their fingers and toes and double the total. But we're so much more sophisticated now, and we can use calculators to count that high, or have our Blackberries remind us.
And if you believe all that, moving a Feast Day to a Sunday because we're all too damned lazy to go to Mass on a weekday (or a weeknight) makes about as much sense.