UNDATED (CNN) -- It happens once in a lifetime. Today is 11-11-11. Lots of people believe it's a lucky day, and there are events taking place to celebrate it, but why? It's the way we're wired.

Las Vegas is always a popular destination for getting hitched. But this week, they've been bracing for even more brides. Clark County, Nevada clerk Diana Alba says, "We've been looking forward to 11-11-11. All year, we knew it would be a very busy day."

11-11-11 is a once in a lifetime date, for most of us. Wedding website The Knot found a huge spike in November 11th nuptials, almost 25,000 couples registered. Look at that compared to other Fridays this month.

Why the rush to the altar, or to buy lottery tickets? Writer Matt Hutson, who's researched the psychology of superstition, says it's the way we're wired. Hutson says, "We all have these innate instincts to try to find patterns in the world and to try to use these patterns to control or predict the future, even if these patterns may not make any logical sense."

Hutson also says it's the things we learn. Some hotels and other tall buildings don't have a 13th floor, simply because for years people have believed the number 13 is unlucky.

It's also the environment we're in. Hutson says, "If you don't feel like you have a lot of control in your daily life, or in a given circumstance you feel anxious, you might rely on other things to try to predict the future."

The tough economy, for example, could be one reason people would be more inclined to cling to the belief that 11-11-11 could be the luckiest day of a lifetime, at least until next December when the calendar reads 12-12-12.