There's a good chance the US Open goes to a playoff for the 34th time in 2017, and that means the year's second major will extend to Monday.
The US Open playoff format isn't sudden death. Rather, it's an 18-hole aggregate-score playoff, meaning that the competitors will play on Monday in search of the US Open trophy. If any players in the playoff are tied after 18 holes, they go to sudden death to determine a winner.
The last time the US Open went to an 18-hole playoff was 2008, when Tiger Woods beat Rocco Mediate on the 19th hole after the pair finished the 18-hole playoff tied. Before that, in 2001, Retief Goosen beat Mark Brooks in a playoff at Southern Hills in Oklahoma. In the history the US Open playoff, there have never been more than three players in the playoff.
The US Open playoff format is the only one remaining in the four men's major championships that isn't less than 18 scheduled holes. The Masters playoff format is sudden death. The British Open Championship playoff format is a four-hole aggregate playoff. The PGA Championship playoff format is a three-hole aggregate playoff.
Even in other USGA championships, the playoff format isn't 18 holes. It's typically now a multi-hole aggregate-score playoff.
What's more interesting is that the US Open has seen the most playoffs in major championship history, with 33. That's 12 more than the British Open, which began 30 years sooner.