The Editor’s Manual
Free learning resource on English grammar, punctuation, usage, and style.
Use commas before and after the year in the American date format (May 1, 2021) but not in British (1 May 2021). No comma is needed when only the month and year are specified (May 2021).
American date format is month-day-year (May 1, 2021); British is day-month-year (1 May 2021). Use commas between day and year in American English; no commas are needed in dates in British English.
To show the exact date, spell out the month, and write the day and year in numerals (May 1, 2021, or 1 May 2021). Don’t place a comma between month and year (May 2021). Spell out the day when it stands alone.
Write years in numerals. Say the year in two parts: the first two and then the second two digits. In words, write the year as it would be pronounced.
BCE and CE are religiously neutral alternatives to BC and AD. While BC, BCE, and CE appear after the date (223 BC), AD appears before (AD 1776). Periods are optional and generally omitted.
Capitalize specific time periods (Middle Ages), but lowercase descriptive terms (medieval times). Also capitalize proper names (Victorian era) and geological time periods (the Jurassic).
Names of decades and centuries (the 1800s, the 1970s, the eighties, the ’90s) are generally considered plural but can also be used with singular verbs.
Centuries are written in either numerals or words (“the 1800s,” “the 19th century,” or “the nineteenth century”). No apostrophe is necessary before the “s” in “1800s.”
Decades may be written in numerals or words (“the 1990s” or “the nineties”), though numerals are preferred in formal texts. In informal usage, an apostrophe may be used to abbreviate the name of a decade.
Spell out single-digit numbers from zero to nine and larger numbers at the start of a sentence. Use numerals with abbreviated units of measurement, to emphasize the exact time, and to write the names of years.