I'm developing an adept for There's no such thing as retirement (aka I've fallen and I can't get up). After searching through the various Shadowrun timelines, I still can't figure out when people started becoming magical. My character was born in 1979. What year would his adept magic have expressed itself?

Magic was always here, it was just very difficult to use. The character could very well have been an adept before the Awakening which began when Ryumyo was sighted on December 24th 2011.

If he had power before the Awakening it was likely limited by several Geasa. His lucky boxers, after confession, must eat soup, pinky rings, ect.

Is it possible for him to have been mundane until 2011, then acquired adept powers?

Technically he wouldn't have been mundane, but could have easily been unawakened until after his powers could show themselves easily. There were many who first showed their magical nature during the early years after the awakening. (and some shortly before)

Adepts gained widespread recognition with the research of Francis Daniels, a fourth dan ki-akkido black belt and the first recorded physad. He was killed in some riots in 2030.

Indications of pre-Awakening physads include Berserkers and legendary martial artists.

In other words, whenever you would like the adept to appear.

-Siege

With Time and dedication, any one who studies martials arts and masters the ability to use KI or Chi i'd say would be a physical adept.

Look at Sifu Buce Lee, if theres any one who was an adept in the real world, he'd be one.

Also, shaolin monks, and the late Mas Oyama are possible candidates.