how time flies
(My,) how time flies.
1. Time has gone by quickly, it is time for me to go. Bill: Look at the clock! Mary: How time flies! I guess you'll be going. Bill: Yes, I have to get up early. John: My watch says it's nearly midnight. How time flies! Jane: Yes, it's late. We really must go.
2. Time passes quickly. (Said especially when talking about how children grow and develop.) "Look at how big Billy is getting," said Uncle Michael. "My, how time flies." Tom: It seems it was just yesterday that I graduated from high school. Now I'm a grandfather. Mary: My, how time flies.
Time moves swiftly onward. Time was said to fly or flee by numerous ancients, especially the Romans, for whom Tempus fugit (translated as “time flies,” although it also means “flees”) was a well-known proverb. Chaucer wrote, “For though we sleep or wake, or rome, or ryde, Ay fleeth the tyme, it nil no man abyde” (The Clerk’s Tale). Occasionally the term was amplified, such as “Time flies as swiftly as an arrow” (in Ken Hoshino’s translation of Kaibaka Ekken’s Ten Kun, 1710). Today we sometimes say, how time flies, occasionally amplified (either seriously or satirically) with when you’re having fun.