Yes, the days of the week must be capitalized in written English: Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, and Saturday. English treats weekday names as proper nouns, so they begin with an uppercase letter in sentences, lists, emails, calendars, and academic writing. The rule remains unchanged when a day is plural or possessive.
Key Facts at a Glance
- Monday and all other weekday names are capitalized in standard English.
- Plural forms remain capitalized: Mondays, Tuesdays, and Fridays.
- Possessive forms remain capitalized: Monday’s meeting and Friday’s deadline.
- Day, weekday, weekend, and week are common nouns and are lowercase in ordinary use.
- Months and holidays are capitalized, while seasons are usually lowercase.
- English capitalization does not automatically transfer to Spanish, French, Italian, or Portuguese.
- Software should use locale-aware date formatting rather than manually changing letter case.
Why Are Days of the Week Capitalized?
Days of the week are capitalized because each weekday functions as the distinctive name of a recurring calendar period. Monday does not mean one unspecified day; it identifies a particular member of the seven-day calendar cycle. That naming function places weekday names in the proper-noun category.
Common nouns identify general classes, such as day, morning, month, and weekend. Proper nouns identify named people, places, institutions, events, or time periods, such as Monday, January, Christmas, and the Middle Ages.
Capitalization is a writing convention, not a claim that weekdays are unique individual objects. Every Monday is still called Monday, just as every January is called January. The repeated occurrence does not make the name common.
Which weekday names require capitals?
All seven English weekday names require an initial capital:
| Weekday | Correct singular | Correct plural | Example |
|---|---|---|---|
| Sunday | Sunday | Sundays | The shop closes on Sundays. |
| Monday | Monday | Mondays | Monday is the first workday for many offices. |
| Tuesday | Tuesday | Tuesdays | Classes meet on Tuesdays. |
| Wednesday | Wednesday | Wednesdays | The report is due Wednesday. |
| Thursday | Thursday | Thursdays | Thursday’s appointment was moved. |
| Friday | Friday | Fridays | Payroll runs on Fridays. |
| Saturday | Saturday | Saturdays | The market opens Saturdays. |
The same rule applies whether a weekday appears at the beginning, middle, or end of a sentence. We arrived on Tuesday, Tuesday begins the conference, and The deadline is Tuesday all use the same uppercase spelling.
How Should Weekdays Appear in Sentences?
Weekday names should begin with a capital letter wherever they occur in a sentence. Sentence position does not affect the rule, so a weekday remains capitalized after a preposition, inside a quotation, or at the end of a sentence.
Correct examples include:
- The interview is scheduled for Monday.
- We usually publish on Wednesday.
- She works late every Thursday.
- “Please call me on Friday,” the manager wrote.
- The store opens earlier on Saturday.
A weekday name can appear beside a lowercase time word without transferring its capital to that word. In Monday morning, only Monday is capitalized because morning is a common noun. The same pattern applies to Tuesday afternoon, Wednesday evening, and Sunday night.
Does capitalization change at the start of a sentence?
No. A weekday is capitalized at the start of a sentence because it is both a proper noun and the first word. The two rules overlap, but the weekday would remain capitalized elsewhere:
- Friday is our busiest day.
- Our busiest day is Friday.
The word day is lowercase in the second sentence because it is a general noun. Writers often overcapitalize nearby time words after correctly capitalizing the weekday.
Do Plural Days Stay Capitalized?
Plural weekday names stay capitalized because adding -s changes number, not noun status. The correct forms are Mondays, Tuesdays, Wednesdays, Thursdays, Fridays, Saturdays, and Sundays.
| Meaning | Correct form | Incorrect form | Example |
|---|---|---|---|
| One named day | Monday | monday | The meeting is Monday. |
| Recurring day | Mondays | mondays | We train on Mondays. |
| Several named days | Mondays and Fridays | mondays and fridays | The clinic operates Mondays and Fridays. |
| Possessive singular | Friday’s | friday’s | Friday’s agenda is attached. |
| Possessive plural | Fridays’ | fridays’ | The Fridays’ schedule changed. |
In ordinary business writing, every Monday and each Monday usually describe a recurring schedule without requiring a plural. On Mondays is equally correct and often more concise.
A common error is to assume that a plural noun becomes lowercase because it describes a category. That reasoning does not apply to names. Americans, Europes, and Mondays retain capitalization even when they refer to multiple instances or members.
What Happens in Compounds and Possessives?
A weekday keeps its capital in compound expressions and possessive constructions, while the attached common noun remains lowercase unless another rule requires capitalization. Examples include Monday morning, Friday afternoon, Monday’s meeting, and Tuesday-to-Thursday schedule.
| Expression | Capitalization | Reason |
|---|---|---|
| Monday morning | Monday morning | Weekday name plus common noun |
| Friday afternoon | Friday afternoon | Weekday name plus common noun |
| Monday’s deadline | Monday’s deadline | Possessive weekday plus common noun |
| Mondays and Wednesdays | Mondays and Wednesdays | Plural proper nouns |
| Monday-to-Friday schedule | Monday-to-Friday schedule | Capitalized weekday names in a compound |
| weekday schedule | weekday schedule | Generic compound, no named day |
The possessive apostrophe does not remove capitalization. Monday’s meeting means the meeting associated with Monday, while Mondays’ meetings refers to meetings associated with multiple Mondays.
Hyphenated expressions require attention to meaning and style. In Monday-to-Friday service, both weekday names are capitalized. In Monday morning, no hyphen is normally needed because the phrase functions as a time expression rather than a permanent compound adjective.
Are Days Capitalized in Titles and Headings?
Days of the week remain capitalized in titles and headings, but other words depend on the chosen heading style. In title case, major words receive capitals; in sentence case, only the first word, proper nouns, and specified names receive capitals.
| Heading style | Correct heading | Main rule |
|---|---|---|
| Sentence case | How to schedule meetings on Monday | Capitalize the first word and Monday |
| Title case | How to Schedule Meetings on Monday | Capitalize major title words and Monday |
| Minimal calendar label | Monday, 9 June | Capitalize the weekday and month |
| All caps design | MONDAY MEETING | Visual style, not ordinary prose |
| Lowercase design | monday meeting | Branding or interface choice, not standard prose |
A publication may use sentence case for article headings and title case for book titles. The style choice changes Schedule, Meetings, or on, but it does not make Monday lowercase.
Official names can preserve unusual capitalization. If a business, event, product, or publication intentionally uses monday.com, Monday Night Football, or another branded form, reproduce the owner’s spelling when referring to that name. Brand styling is an exception created by the proper name, not a change to the ordinary English rule.
Which Time Words Stay Lowercase?
Generic time words such as day, week, weekday, weekend, morning, and season are lowercase unless they begin a sentence or form part of an official name. Capitalizing a nearby weekday does not create a capitalization requirement for these common nouns.
| Time word | Default form | Capitalized example | Lowercase example |
|---|---|---|---|
| day | lowercase | Day One, official title | a busy day |
| week | lowercase | Holy Week, named observance | next week |
| weekday | lowercase | Weekday, sentence opening | a weekday schedule |
| weekend | lowercase | Weekend, sentence opening | this weekend |
| morning | lowercase | Morning Edition, title | Monday morning |
| season | lowercase | Season 2, named series label | spring season |
The sentence I cannot wait for the Weekend is incorrect in ordinary prose. The correct version is I cannot wait for the weekend. The word weekend is not a proper noun merely because it refers to a familiar part of the calendar.
The same principle applies to day in day off, workday, and day of the week. These expressions describe general concepts rather than naming a particular day.
How Do Months, Seasons, and Holidays Compare?
Months and named holidays are capitalized, but seasons are lowercase in most ordinary English writing. The difference comes from naming status: January names a calendar month, while winter generally describes one of four seasons.
| Time category | Default capitalization | Correct examples | Common error |
|---|---|---|---|
| Weekdays | Capitalized | Monday, Saturday | monday, saturday |
| Months | Capitalized | January, October | january, october |
| Seasons | Lowercase | spring, summer, autumn, winter | Summer, Winter |
| Holidays | Capitalized | Thanksgiving, Labor Day | thanksgiving, labor day |
| Historical periods | Usually capitalized | Renaissance, Middle Ages | renaissance, middle ages |
Seasons may be capitalized when they appear in an official title, branded event, or formal name. The Winter Olympics and Spring Semester 2026 follow the capitalization conventions of named programs or events, although a publication’s house style may vary for generic academic terms.
Holiday names preserve capitals in multiword forms. Correct examples include New Year’s Day, Martin Luther King Jr. Day, Independence Day, and Good Friday. The word day is capitalized in these examples because it belongs to the official holiday name.
Is “day of the week” capitalized?
No. The standard phrase is day of the week, with day, week, and the preposition of lowercase. A named weekday inside the phrase is capitalized: Monday is my favorite day of the week.
Do Major Style Guides Agree?
Chicago style, AP style, MLA style, and APA style all capitalize English weekday names. Their differences concern date punctuation, abbreviations, numerals, headings, and reference formatting rather than whether Monday begins with a capital.
| Style system | Weekday example | Related date tendency | Practical use |
|---|---|---|---|
| Chicago Manual of Style | Monday | Often spells out months in prose | Books, scholarly publishing |
| Associated Press style | Monday | Compact journalistic dates | News and public communications |
| MLA style | Monday | Day-month-year works cited patterns | Humanities writing |
| APA style | Monday | Structured dates in references | Social and behavioral sciences |
| General business English | Monday | Depends on company convention | Emails, reports, calendars |
A style guide can prefer Mon. in a table, Monday in running prose, or a particular date order. None of those formatting choices authorizes monday in standard English sentences.
The practical rule is simple: follow the publication’s date and abbreviation policy, but retain the uppercase initial for a fully written English weekday.
Does Regional English Change the Rule?
British, American, Canadian, Australian, and New Zealand English generally capitalize the names of the days of the week. Regional differences usually affect date order and punctuation, not the weekday’s initial letter.
For example:
- American English often writes Monday, June 10, 2024.
- British English commonly writes Monday 10 June 2024.
- ISO 8601 uses a numeric form such as 2024-06-10, which avoids a written weekday.
- Both written English varieties use Monday, not monday.
The date format can influence whether a comma appears, whether the month comes before the day, and whether ordinal endings are used. It does not normally alter the capitalization of Monday, Tuesday, or the other weekday names.
Does the Rule Change in Other Languages?
The English capitalization rule does not apply universally across languages. Spanish, French, Italian, and Portuguese normally write weekday names in lowercase, while German capitalizes them because German nouns are capitalized.
| Language | Sunday | Monday | Typical rule |
|---|---|---|---|
| English | Sunday | Monday | Capitalized |
| Spanish | domingo | lunes | Lowercase |
| French | dimanche | lundi | Lowercase |
| Italian | domenica | lunedì | Lowercase |
| German | Sonntag | Montag | Capitalized |
Translation requires more than changing the first letter. A bilingual calendar, website, or application must use the target locale’s date conventions, weekday order, abbreviations, and grammatical forms.
A Spanish interface that displays Lunes may be incorrectly localized even if the English interface correctly displays Monday. Conversely, converting English Monday to lowercase is correct only when the target language’s standard convention requires it.
How Are Days Abbreviated?
Weekday abbreviations are capitalized because they remain shortened forms of capitalized names. The exact abbreviation and punctuation depend on the style guide, publication, calendar width, or software locale.
| Full name | Common abbreviation | Compact calendar form | Example |
|---|---|---|---|
| Sunday | Sun. | Sun | Sun., 14 July |
| Monday | Mon. | Mon | Mon., 15 July |
| Tuesday | Tue. or Tues. | Tue | Tue., 16 July |
| Wednesday | Wed. | Wed | Wed., 17 July |
| Thursday | Thu. or Thurs. | Thu | Thu., 18 July |
| Friday | Fri. | Fri | Fri., 19 July |
| Saturday | Sat. | Sat | Sat., 20 July |
Many calendars omit periods because the interface defines the abbreviation as a display label. In running prose, a publication may prefer Mon. or the full Monday. Writers should avoid mixing systems within one document.
Do not assume that a shortened form can be lowercase. mon, tue, and fri may appear in a stylized interface or file naming system, but they are not standard sentence forms.
How Should Software Handle Weekday Names?
Software should generate weekday names through locale-aware date-time functions rather than applying a universal English capitalization rule. English output normally returns Monday, while French output may return lundi and Spanish output may return lunes.
Python can produce a localized or system-configured full weekday with the %A directive:
from datetime import date
print(date(2024, 6, 10).strftime("%A"))
On an English locale, the result is typically Monday. The result depends on the active locale and operating-system configuration, so a developer should not assume that every environment returns the same language.
JavaScript’s Intl.DateTimeFormat supports locale-sensitive formatting:
const date = new Date(Date.UTC(2024, 5, 10));
new Intl.DateTimeFormat("en-US", {
weekday: "long",
timeZone: "UTC"
}).format(date);
The expected English result is Monday, while a French locale can produce lundi. Locale-aware formatting is better than calling a generic capitalization method because capitalization, language, abbreviations, and grammatical conventions vary together.
Is capitalization the same in data and prose?
No. A database may store weekdays as numeric values, lowercase keys, or standardized codes such as ISO weekday numbers. Those machine representations do not determine how the value should appear in user-facing English text.
A developer can safely store 1 for Monday or monday as an internal key if the application’s schema requires it. The rendered English label should still be Monday unless the interface intentionally uses a different visual convention.
Are There Exceptions to Weekday Capitalization?
Ordinary English has very few exceptions. A lowercase weekday usually indicates a typographical error, a deliberate brand style, a code value, a language other than English, or a visual design system rather than standard grammar.
The main situations requiring separate treatment are:
- Official brand styling: A company may legally style its name in lowercase.
- Programming data: Internal values may use lowercase strings.
- Non-English text: Spanish and French normally use lowercase weekdays.
- Quoted unusual spelling: Reproduce a source exactly when analyzing its wording.
- Graphic design: A poster may use all lowercase for visual effect.
- File and URL conventions: Technical systems often normalize text to lowercase.
These cases do not overturn the English grammar rule. They identify contexts where the text is not ordinary English prose or where another authority controls the spelling.
An editor should distinguish a deliberate lowercase treatment from an accidental error. If the word appears in an email sentence, report, essay, or article without a stated style reason, capitalize it.
What Are the Most Common Weekday Errors?
The most common errors involve extending the capital from a proper noun to an adjacent common noun, or removing the capital when a weekday becomes plural. A reliable correction keeps the weekday uppercase and checks each neighboring word independently.
| Incorrect form | Correct form | Explanation |
|---|---|---|
| We meet on monday. | We meet on Monday. | Monday is a proper noun. |
| The office closes on Fridays. | The office closes on Fridays. | Plural days remain capitalized. |
| I dislike the Weekend. | I dislike the weekend. | Weekend is a common noun. |
| See you Monday Morning. | See you Monday morning. | Morning is lowercase in a generic phrase. |
| Our Friday’s meeting moved. | Our Friday meeting moved. | Remove the unnecessary possessive. |
| The report is due every friday. | The report is due every Friday. | Every does not change capitalization. |
One especially frequent mistake is unnecessary possessive marking. Friday meeting identifies a meeting occurring on Friday, while Friday’s meeting identifies the meeting as associated with Friday. Both can be grammatical, but they express slightly different structures.
Another mistake occurs in schedules copied from spreadsheets. Calendar software may use MON, Mon, or mon as a display format. Copying that label into formal prose without checking the surrounding style can produce inconsistent capitalization.
What Is the Fastest Editing Check?
To proofread weekday capitalization, search for all seven weekday stems, then inspect compounds, plurals, abbreviations, and nearby common nouns. A five-step check usually catches the relevant errors in a short document.
- Search for mon, tue, wed, thu, fri, sat, and sun.
- Capitalize complete English weekday names and their plural forms.
- Check possessives such as Monday’s and Fridays’.
- Lowercase generic terms such as day, weekend, morning, and season.
- Compare abbreviations with the publication’s chosen style.
For a report, also scan headings, tables, captions, calendar labels, and email subject lines. These locations often use a different visual style, but a fully written weekday should still be recognizable as Monday, not monday, unless a deliberate design or brand rule applies.
A useful practitioner rule is to separate the named unit from its category: Monday is the name, while day is the category. Capitalize the name and evaluate the category under ordinary common-noun rules.
FAQ
Should “Monday” be capitalized in an email?
Yes, Monday should be capitalized in a professional or personal email because it is an English weekday name. Write I will send the invoice on Monday, Monday’s meeting is confirmed, and Please respond by Monday. Email subject lines may use sentence case, title case, or a company style, but the weekday remains capitalized.
Should you capitalize days of the week in a resume?
Yes, capitalize weekday names in a resume, cover letter, or application. Examples include Available Monday through Friday, Worked Saturdays, and Scheduled interviews on Tuesdays. Resume design may use uppercase labels such as MON-FRI, but standard sentence text should use Monday through Friday.
Is “Friday night” capitalized?
Only Friday is capitalized in the ordinary phrase Friday night. Friday is a proper noun, while night is a common noun. The same pattern applies to Saturday morning, Sunday afternoon, and Wednesday evening, unless the entire phrase belongs to an official title.
Should “every Monday” use a capital letter?
Yes, write every Monday with a capital M. The determiner every does not change the status of the weekday name. The alternative on Mondays is also correct, and the plural Mondays remains capitalized.
Are weekdays capitalized in APA references?
Yes, a fully written weekday remains capitalized in APA writing and references. APA may prescribe a particular date structure for a source, publication, or retrieval statement, but those formatting requirements do not turn Monday into monday. Follow APA punctuation and date-order rules separately.
Should “weekdays” be capitalized?
No, weekdays is normally lowercase because it is a common noun meaning the general category of days from Monday through Friday. Write The service operates on weekdays. When naming the specific days, write Monday through Friday, with both weekday names capitalized.
The Bottom Line
The answer to should the days of the week be capitalized is yes: standard English capitalizes Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, and Saturday in every ordinary sentence. Plurals and possessives retain the capital, while related common nouns such as day, weekday, weekend, morning, and season usually remain lowercase. Use local language and locale-aware software rules when writing outside English.
