I spent a little time looking up some details about this, and thought what I found might be of practical use to those who are interested.
A bishop (not a priest) can give a dispensation from the Lenten obligation to abstain from meat on Fridays. It's commonly believed that local bishops grant such dispensations when St. Patrick's Day and/or St. Joseph's Day fall on a Friday during Lent, but in fact, as a canon lawyer might put it, "the general law of abstinence does not bind on solemnities." St. Patrick's Day is not a solemnity; St. Joseph's Day is. So a dispensation from the Lenten obligation of abstinence would be required to eat meat on St. Patrick's Day if it fell on a Friday, but would not be required on St. Joseph's Day if it fell on a Friday. In other words, it goes without saying that the abstinence rule doesn't apply to St. Joseph's Day. In granting a dispensation for St. Patrick's Day, bishops often ask for observance of another day of penance and abstinence at some other time during the week. In 2013, neither falls on a Friday.
Here's something about Lent I didn't know until just a few years ago (some of us children of the Sixties were, let's just say, "poorly catechized"; it's all been self-taught home schooling since then), a Lenten sacrifice is to be honored during the 40 days of Lent, that is to say, the 40 days between and including Ash Wednesday and Holy Saturday that are NOT Sundays. This year, for example, there are 46 days between and including Ash Wednesday and Holy Saturday; only the 40 non-Sunday days are the 40 days of Lent. The Sundays of Lent are solemnities, and neither abstinence nor sacrifice is binding on these days. Practical significance: you're free to eat candy or drink soda or smoke cigarettes or gossip about your coworkers or do whatever else you said you'd give up for Lent on the Sundays during Lent, with a clear conscience (well, maybe not so much for the gossip, but surely for the rest). However, if you're also trying to break a bad habit, you probably would want to try to avoid availing yourself of the Sunday loophole.
"Your swimming suit matches your eyes, you hold your nose before diving, loving you has made me bananas!"