When Nick Calas first started coming to help out at the Park City Senior Center, Cheryl Soshnik, vice president of the center’s board of directors, was surprised. Calas looked too young. “I said, ‘I was born in ’59. Do the math,’” he said, smiling. Calas is always smiling. That youthful, ear-to-ear demeanor belies the truth: Calas is indeed a senior. But he’s also emblematic of the spry, eager attitude that defines those who volunteer at the center.