Tim Hortons employee Pinky Lung tells another customer that coffee is on the house after a mystery man pays for 500 cups and leaves. (CBC)

It was coffee on the house all day Monday after a young man walked into a Tim Hortons on Jasper Avenue and paid for one day's worth of coffee — about 500 cups.

"We asked him his name and he didn't tell us," hostess Pinky Lung told CBC's Lisa McGregor. "He said he didn't want to tell anyone."

But as McGregor reports, the mystery man's act of kindess made a lot of people's day.