By Vanessa Heaney
BBC News, Washington
For many people it was just another Saturday, but for the superstitious it was a very lucky day.
For the superstitious, the number seven has ancient significance
It was the seventh day of the seventh month of the seventh year of the millennium. Bookmakers had braced themselves for an influx of bets.
Wedding venues and bridal suites were completely booked up across the US.
Triple sevens mean big bucks on the jackpot - and thousands of couples were betting that it would bring good luck to their marriage, too.
Never before has there been this much demand to get married on a certain date.
As many as 70,000 couples were estimated to have tied the knot.
Cake makers, florists and wedding planners went into overdrive, organising seven-tiered cakes and seven-course meals.
In Orange County, California, the register office opened up additional venues, bringing in extra staff and offering couples time slots ending in the number seven.
The number seven has ancient religious and cultural significance.
The Greek philosopher Pythagoras called it the perfect number and 13th-Century Italian writer Dante Alighieri used it frequently in his work.