NEW YORK - For the first time, a billion people used Facebook in a single day on Monday.

CEO Mark Zuckerberg marked the occasion with a post on his Facebook page, saying that one out of seven people on Earth logged in to the social network to connect with their friends and family. 

The 1 billion figure is different from the daily user numbers Facebook discloses each quarter when it reports its financial results. Those are the average number of daily users, counted over a 30-day period. Facebook had 968 million daily active users in June. 

Overall, Facebook has nearly 1.5 billion users who log in at least once a month. It hit the 1 billion user milestone in October 2012. Most people on Facebook live outside the U.S. and Canada.