Jay Z asked him to pick out a watch for his two Carnegie Hall concerts last year (he wore a Jaeger-LeCoultre Reverso).

John Mayer brought him backstage after a Jones Beach concert last summer to talk about Mr. Mayer’s latest acquisition (a Tiffany-inscribed Paul Newman-model Rolex Daytona).

Time magazine named his watch-enthusiast site, Hodinkee, one of its 50 best websites for 2013.

Since founding the site as a hobby in 2008, Benjamin Clymer, a former UBS project manager, has emerged as a high priest to a growing cult of young mechanical-watch lovers that includes whiskered heritage-brand devotees, fashion-forward Wall Street analysts and more than a few celebrities.

Celebrities even make up its list of contributors. Mr. Mayer is a regular columnist for the site; J. J. Redick, the Los Angeles Clippers guard, has appeared in a video; and Fred Durst, the Limp Bizkit frontman, is a frequent commenter on its Instagram feed.