I can eat meat any day of the week.

It's only a custom held by Roman Catholics. It isn't binding in any way. Just an abstention from red meat on the day when Jesus' flesh was torn for humanity.

Stipulating that this is a Catholic custom only (except for the last bit at the end): In Ye Olden Days, meat from land animals was a luxury food. Very expensive, mostly eaten by rich people. Fish was what poor people ate, since anyone could catch fish (with a piece of string and a bent pin with a bug on it). The Bible tells us that Christianity was started by a guy who believed that wealth was a sign that you weren't all that moral, so if you were poor you were holier. So for many many centuries, one day a week, Friday, was a day on which everyone had to eat fish, and no one could eat meat, to put everyone on the same level for a day. During Lent no one could eat meat at all (about 40 days without a steak). Only in the 20th Century was this changed to "no meat on Fridays only during Lent" in Vatican II. Grandma was pre-Vatican II. One day in June about six years ago we offered to take her off the Central Kansas farm and out to a fancy restaurant in a nearby bigger city ("Pop. 50,000 and growing!"). This turned into a spirited roundtable discussion amongst the cousins because it was a Friday and she had *never* eaten meat on a Friday. Central Kansas, a landlocked region, is not known for its fish dishes. Eventually we found a place which had fresh salmon airlifted in on Fridays. Now, this rule is merely doctrinal and not set in stone (provided you are a post-Vatican II Catholic), so dispensations and odd rules have been added over the years. For example, Irish-Americans have grown used to "corned beef and cabbage" for St. Patrick's Day supper. St. Patrick's Day occurs during Lent. In 2000 and 2006, St. Patrick's Day fell on a Friday, which would have nixed the traditional Irish-American "corned beef and cabbage". Realizing which side their Irish soda bread was buttered on, American Bishops granted dispensations in those two years for the consumption of "corned beef and cabbage" on the Friday St. Patrick's Day celebrations. The next time this same dispensation will have to be granted is in 2017. Another interesting detail about "no meat on Fridays" deals with religion's unfortunate disconnect between itself and "reality". Thanks to some odd Catholic Papal ideas about what constitutes an "aquatic fish", the following types of meat are defined as "fish" for the purpose of "no meat on Fridays": beaver; capybara (a large South American water-dwelling rodent); muskrat (Canada and the Northern U.S.); sea turtle; and iguana (the desert used to be underwater, dontcha know). Finally, England's government was firmly Protestant/Anglican during the reign of Queen Elizabeth I, but that didn't stop the strong Catholic feelings. Nor, apparently, did it stop the rule prohibiting the consumption of meat on all Fridays. Lord Burleigh, Queen Elizabeth's most trusted advisor, kept the rule in place even after she brought England back to Protestantism, because he didn't want the fishmongers to suffer. This last bit was immortalized in Shakespeare's "Hamlet" during an exchange between Polonius and Hamlet, where Polonius asks if Hamlet knows who he is and Hamlet (acting insane) refers to Polonius as a fishmonger. Since Polonius has often been considered by Shakespeare scholars as a poke at Lord Burleigh, this is a comment on Lord Burleigh's retention of the "no fish on Fridays" rule to protect the fishmongers.