The hacking seconds function (or complication) stops the watch’s second hand whenever the crown is pulled out for the purposes of setting the time. This function was developed in the 20th century to aid in the synchronization of a watch and is found on many different kinds of watches today.
How does hacking seconds work? Here’s a basic explanation. When the crown is pulled out, a brake lever makes direct contact with the balance wheel which immediately stops the watch.
For those of us who love to make sure our watches are in exact sync with the NIST-F1 atomic clock or like to have all of our watches showing the exact same time down to the seconds, the hacking seconds function is your best friend.
In 2008, the German brand A. Lange & Söhne took this function to the next level. Not only did they make it work with a tourbillon, but they further enhanced it with a zero-reset mechanism. This stops the seconds hand and returns it to zero. Pretty neat.
And that is the hacking seconds function in a nutshell.