Rolex Cosmograph Daytona 116500LN (photo: Rolex)

The instructions below are applicable to any Rolex Daytona manufactured after the year 2000, like the 116500LN shown in the photo above, with a Rolex movement and screw down pushers. The Daytonas released prior to this date are equipped with an El Primero Zenith movement that has a different configuration of the sub-dials.

Using the Chronograph Function
First, unscrew the pushers located at the 2 and 4 o'clock positions. If the long, thin seconds hand is not at 12, hit the pusher at 4 o'clock to reset. The chronograph function is initiated by hitting the pusher at 2 o'clock once. This will get that seconds hand moving around the dial. Once one minute has elapsed, the sub-dial at 3 o'clock will mark it. Once an hour has passed, the sub-dial at 9 o'clock will mark it. (The sub-dial at 6 o'clock is used to keep the seconds on the clock, not the chronograph.)

Using the Tachymeter
The numbers printed on the bezel of the Daytona are to measure the average miles per hour a race car driver goes per mile on a race track. As you can see, there is a 60 at 12 o'clock, meaning that if you travel a mile in one minute, you are traveling at 60 miles per hour (there are 60 minutes in an hour, after all). To measure your average speed per mile, hit the pusher at 2 o'clock to start and hit it again to stop it right when you reach one mile traveled. Wherever the chronograph seconds hand lands on the bezel would indicate the amount of miles you would travel in an hour at that speed.

While chronograph and tachymeter functions seem superfluous in an era where you can keep time and measure speed on your smartphone (and now smartwatch), the sub-dials and numbers printed on the bezel fill the space nicely and harken back to the 1960s when these watches became popular. Like many classic watches, chronometers offer more in the way of aesthetic and legacy these days than they do in terms of functionality. However, they possess a charm that is hard for horology buffs to resist.

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