Zero. Light years are a measure of distance, not time.
Twenty years
1.67 years
1.64597995 × 1014 miles
"How many light years does Dschubba have?" "How many light years does Dschubba have?"
One generation is twenty years.
One generation is twenty years.
twenty years
two
Twenty..
20 years is 175,200 hours
Twenty years
1.4 years