years

correct: Flock of Seagulls was a popular band in the ’80s.
incorrect: Flock of Seagulls was a popular band in the 80's.

Note the "right-handed-ness" of the quote in the first sentence. Many word processors are confused and default to the left-handed single quote. It's a pain, but type both single quotes and delete the first one. Or use the shortcut key to the right-handed version.