For the first time, a billion people used Facebook in a single day on Monday. Facebook’s chief, Mark Zuckerberg, observed 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 one 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. Most people on Facebook live outside the United States and Canada.