The new Antarctic 35mm takes inspiration from a 1950s Nivada Grenchen of the same name. In the mid-'50s, the U.S. began a series of missions to Antarctica, called "Operation Deep link Freeze." Admiral Richard Byrd oversaw the operations – on his wrist was a Nivada Grenchen (Croton) Antarctic. You can see link the exact same watch in period advertising link like this one:

We all know that months and years vary in length, adding complication to any calendar. Standard perpetual calendars account for leap years and the length of individual link months. This would be fine if a year were 365.25 days (requiring adjustment every 4 years). But in reality, a year is 365.2425 days, meaning years ending in 100, 200, and 300 aren't leap years, while years divisible evenly by 400 are leap years. That means standard perpetual calendars will require adjustment once every 100 years.