Now, it's time for Words and Their Stories -- our weekly program about common, everyday expressions in American English.Today we are talking about the somewhat unusual day of February 29.It comes up on the calendar only every four years.A year with a February 29 might be good news if you are paid by the day or the week.But it might be bad news if you were born on a February 29.You have to wait three years in between birthdays!In any case, American English has a term for the unusual situation.February 29 is called a leap day.And the entire 12 month period with a February 29 in it is called a leap year.This year, 2020, is such a year.As a verb, the word "leap" means to jump, or to move quickly."Leap" can also be a noun, meaning a jump, or a sudden move.In a leap year, the dates jump over one day of the week.Let me explain.In 2017, the last day of the year, December 31, fell on a Sunday.In 2018, it fell on a Monday.In 2019, it fell on a Tuesday.But in 2020, December 31 will fall on a Thursday.It just leaped right over Wednesday.The reason for a leap day or a leap year is because our calendar does not follow the Earth's orbit around the sun exactly.Each year, we have a little time left over.So every four years, we put all that time together into an extra day – or, what is officially called an intercalary day.But I have never, ever heard an English speaker use that term."Leap day" is fine."Leap" is also an important word for two other common – but opposing – American expressions.One is a kind of warning.If you want someone to investigate a situation completely before taking action, you might say, "Look before you leap."The other expression is a phrase of hope.Urging someone to "take a leap of faith" invites the person to take action, even if not everything about a situation is known.Interestingly, both phrases are completely reasonable to say to someone who is about to get married.On that note, some people choose to marry on February 29 because it is an unusual date.One wedding chapel in the U.S. city of Las Vegas is even offering a free ceremonyfor those who decide to "take the leap" into marriage on the last day of this month.The ceremony is followed by a chance to skydive together – that is, jump out of an airplane with a parachute.But some ancient peoples would likely tell couples not to do it.Leap years were believed to be difficult, and leap days unlucky and a bad time to begin anything new.Whatever you think about them, the change in the calendar will be gone soon enough.Then we can return to normal, and leap over February 29 as usual.