John Clayton Mayer turns 46 years old today. Here are five things you may not have known about the singer. 1. Mayer was inspired to play guitar after watching Michael J. Fox's guitar solo in 'Back to the Future'. 2. He once broke his Grammy award for Song of the Year in half to split with Alicia Keys. 3. Mayer has a watch collection worth millions of dollars. 4. After he was diagnosed with cardiac dysrhythmia and spent time in the hospital, he began writing songs. 5. He has an “SRV” tattoo in honor of late guitarist Stevie Ray Vaughan.