1. Use figures for decades: the 1990s, the ’90s, the mid-1990s. 2. Use an apostrophe before the decade if abbreviated as in the ’80s, the turbulent ’60s. 3. Spell out the decade when used at the beginning of a sentence: Nineteen-eighties business models are no longer sufficient. 4. Follow the “less than 10” as in the fifth century, the 15th century, mid-eighth century, mid-12th century, ninth-century literature, 17th-century poets. 5. B.C. follows the year or century as in 88 B.C. […]