Missing definite article in the date

Missing or misplaced "the" can make dates sound nonnative or change meaning. Below are concise rules, clear examples, and ready-to-use rewrites for decades, ordinal-day dates, holidays and short forms like '90s.

Quick answer: when to use "the"

Add "the" for decades and for ordinal-day forms that use "of" (the 1990s; on the 24th of November). Don't add "the" before bare years (in 1999) or most holiday names (Valentine's Day, Christmas).

Decades: in the 1990s, in the 2000s → include "the".
Ordinal + of: on the 3rd of May; the 24th of November → include "the".
Bare years: in 1999, in 2015 → no "the".
Holidays: Valentine's Day, Christmas → usually no "the" unless you mean a specific occurrence (the Christmas of 1995).

Core explanation: the short rules you need

Keep this checklist in mind:

Decades: use "the" - the 1990s, the '80s.
Ordinal + "of": use "the" - on the 24th of November.
Bare year: no "the" - in 1999, in 2015.
Holidays: no "the" for the event name - celebrate Christmas. Use "the" only when you mean that particular occurrence.
Prepositions: use in for spans (in the 1990s), on for days (on the 24th of November), at for some events (at Easter/at the weekend depending on variety).

Examples: common wrong → right pairs

Scan these and adopt the right-hand version when editing your text.

Wrong: She grew up in 1990s.
Right: She grew up in the 1990s.
Wrong: The conference is in 24th of November.
Right: The conference is on the 24th of November.
Wrong: We celebrate the Valentine's Day every year.
Right: We celebrate Valentine's Day every year.
Wrong: Sales dropped in 2000s after the crash.
Right: Sales dropped in the 2000s after the crash.
Wrong: Back in 90s we relied on dial-up.
Right: Back in the '90s we relied on dial-up.
Wrong: My flight departed 24th November last year.
Right: My flight departed on the 24th of November last year.
Wrong: They met on the Easter.
Right: They met at Easter.
Wrong: History of 18th century is complex.
Right: History of the 18th century is complex.

Real usage: work, school and casual examples

Choose the form that fits your audience: formal notices often use full ordinals and "the"; casual speech can use shortened decades.

Work: Please note: the Q3 report compares figures with the 1990s.
Work: The project kickoff is on the 2nd of June; calendar invite sent.
Work: We will analyze trends from the 2000s in tomorrow's presentation.
School: In the 1960s, migration patterns changed dramatically.
School: The treaty was signed on the 11th of November 1918.
School: Cite studies from the 1980s that examine early personal computing.
Casual: I grew up in the '90s - best cartoons ever.
Casual: My birthday is on the 24th of November - come by after 7?
Casual: We went to that festival in the 2000s; it was tiny compared with now.

Rewrite help: fix your sentence in three steps

Quick checklist: identify the date type, apply the rule, then confirm the preposition.

Templates: "in the [decade]" | "on the [ordinal] of [Month]" | "[Holiday name]" (no "the").
Rewrite:
Wrong: I grew up in 1990s. → I grew up in the 1990s.
Rewrite:
Wrong: The meeting is 24th April. → The meeting is on the 24th of April. (Or: The meeting is April 24.)
Rewrite:
Wrong: We celebrated the Christmas last year. → We celebrated Christmas last year. (Or: the Christmas of 2019 when specifying the year.)
Rewrite:
Wrong: Published in 80s fashion. → Published in the 1980s. (Or: published in '80s fashion → the '80s.)
Rewrite:
Wrong: She was born in July 5th. → She was born on July 5th. (US) or on the 5th of July (UK).

Try your own sentence

Test the whole sentence, not just the phrase. Context usually makes the right choice obvious.

Hyphenation, apostrophes and decades

Short form uses an apostrophe for omitted digits: the '90s. Full numerals use no apostrophe: the 1990s. When the decade becomes an adjective, hyphenate the compound.

Correct: the '90s; the 1990s.
As an adjective: nineteen-nineties-inspired fashions (hyphenated).
Avoid: in 90s - use the '90s or the 1990s.

Spacing and ordinal-number style (24th of November vs 24 November)

Pick one style and stay consistent: UK tends to use "24 November" or "the 24th of November"; US prefers "November 24" or "November 24th". If you use "of", include "the".

UK: on 24 November OR on the 24th of November (include "the" with "of").
US: on November 24 or on November 24th (no "of").
Decades: both varieties use "the": the 1990s.

Memory trick & quick test

Mnemonic: "Decades & Ordinals take The; Holidays Don't." Make a two-step test: is it a decade? add "the". Is it an ordinal with "of"? add "the". Otherwise, likely no "the".

Test: "in 1970s" → decade? yes → in the 1970s.
Test: "on 5th of May" → ordinal + of? yes → on the 5th of May.
Test: "Christmas is coming" → holiday? yes → Christmas (no "the").

Similar mistakes and quick grammar checks

Missing "the" with dates commonly co-occurs with other article and preposition errors. Apply the same quick checks.

Centuries: use "the" - in the 18th century.
Weekend: UK uses "at the weekend"; US prefers "on the weekend".
Institution names: some drop "the" (Harvard University) while generic uses take it (the university).
Parts of day: in the morning vs at night (no "the" for general night, but the night of the 4th when specific).

Usage: Wrong: She lived in 18th century. →
Right: She lived in the 18th century.
Usage: Wrong: Meeting at weekend. → Right (UK): Meeting at the weekend. Right (US): Meeting on the weekend.
Usage: Wrong: The Harvard is famous. →
Right: Harvard University is famous. (But: the university was founded in 1636.)

FAQ

Do I say in 1990s or in the 1990s?

Use in the 1990s. Decades normally take the definite article. You can also write the '90s or the 1990s in full.

Is it wrong to write 24th November without "the"?

Not always - 24 November is standard British style. If you include "of" (the 24th of November), include "the." Be consistent within a document.

Should I say "the Valentine's Day" or "Valentine's Day"?

Use Valentine's Day without "the." Add "the" only when referring to a particular occurrence: the Valentine's Day we remember from 1999.

How do I write decades in formal writing?

In formal writing, include "the": the 1990s. If you spell the decade out as an adjective, hyphenate the compound: nineteen-nineties-inspired design.

What quick check tells me whether to add "the"?

Ask: am I naming a decade or an ordinal-day date with "of"? If yes, add "the." If it's a bare year or a holiday name, don't add "the."

Want to fix a sentence fast?

Paste your sentence into a grammar checker or apply the rewrite templates above. Small changes-adding or removing "the" and the right preposition-usually make the sentence correct and natural.

Copy a rewrite example, swap the month or decade to match your sentence, and you'll often fix the problem in under a minute.