A gremlin minute?

Got a cookbook at the used book store, printed in 1966: "Uncle John's Original Bread Book" [1]

For St. Patrick's Day Oatmeal Bread we have ...

Spoon mixture into large greased bread pan and bake in 350° F. oven for 70 gremlin minutes;

What in the Wide World of Sports is a gremlin minute?

[1] By John Rahn Braue, copyright 1961.