How the wristwatch went from a lady's trinket to a soldier's lifeline in WWI

Zero Hour: Telling time was a matter of survival and strategy during WWI (2014)

Before World War I, telling time was a matter of church bells and sunrises; a wristwatch was a jeweled bracelet for women. The war changed that. With armies dug in across hundreds of miles, officers had to synchronize watches to launch attacks, and the phrase "zero hour" entered the language. Rolex and other watchmakers raced to build rugged, luminous trench watches, while advertising rebranded the accessory as manly. The armistice itself was set for 11 a.m. on 11/11/1918.