Riddle

A man is talking to God.
The man: "God, how long is a million years?"
God: "To me, it's about a minute."
The man: "God, how much is a million dollars?"
God: "To me it's a penny."
The man: "God, may I have a penny?"
God: "Wait a minute."




Question: What comes once in a minute, twice in a moment, but not once in a thousand years?