leap lent
For a Catholic, not observing Lent every 7th year or so. Real Lent is not really 40 days and 40 nights since it doesn't include the 6 Sundays that occur during it. So, you can skip Lent on the 8th year because you have "made up" for the 40 days by observing 46 days the previous 7 years. It is like a leap year, except for Lent. For instance, observe Lent for 2010 - 2016 and observe Leap Lent for 2017. The extra 2 days can be used differently depending on the Leap Lent observer.
