Afternoon Abbreviation: Standard Shortforms, Style Rules, and Time Conventions

The standard abbreviation for "afternoon" in time references is p.m. (or PM), which stands for the Latin phrase post meridiem, meaning "after midday." When shortening the word "afternoon" itself in written text, calendars, or informal notes, the accepted abbreviations are aft. or aftn.

Understanding how to abbreviate "afternoon" depends entirely on the context of your sentence. If you are designating a specific time of day on a 12-hour clock, you must use p.m. (or one of its accepted typographic variants like PM or p.m.). If you are referring to the noun "afternoon" as a block of time within a schedule, log, or note, textual shortenings such as aft. or aftn. are appropriate.

This comprehensive guide breaks down the Latin origins of timekeeping abbreviations, exact style guide requirements from major publishing standards, common punctuation errors, and alternative regional terms.

The Primary Time Abbreviation: "p.m." (post meridiem)

When expressing time on a 12-hour clock, the designation for the afternoon and evening hours is p.m. (often written as PM, p.m., or PM depending on the editorial style guide).

Etymology and Historical Origin

The term p.m. originates from the Latin phrase post meridiem.

• Post translates directly to "after."
• Meridies translates to "midday" or "noon."

The Latin word meridies itself derives from medius (middle) and dies (day). Therefore, post meridiem literally signifies the period occurring after the sun crosses the local meridian—the highest point of its arc across the sky.

The counterpart to post meridiem is ante meridiem (a.m.), which translates to "before midday." The dual division of the solar day into two 12-hour blocks has been in practice since ancient Egyptian and Roman civilization, though modern mechanical and atomic clocks standardized the exact split at 12:00 noon.

The Exact Range of p.m.

The p.m. period begins immediately after 12:00:00 noon and continues until 11:59:59 at night:

• 12:00:01 p.m. is unambiguously in the afternoon.
• 11:59:59 p.m. is the final moment of the post meridiem period before midnight.

The 12:00 Ambiguity: Noon vs. Midnight

A long-standing point of confusion in time notation is whether 12:00 in the middle of the day should be designated as 12:00 a.m. or 12:00 p.m.

Etymologically, 12:00 exact solar noon is neither ante meridiem (before noon) nor post meridiem (after noon); it is the meridies itself. Because of this technical ambiguity, standards organizations like the National Institute of Standards and Technology (NIST) recommend avoiding "12:00 p.m." in legal, aviation, or technical documents where absolute clarity is required.

Instead, best practices dictate writing 12:00 noon (or simply noon) for midday, and 12:00 midnight (or midnight) for the start/end of the day. However, in standard digital clocks, computer operating systems, and general communication, 12:00 PM is universally configured to represent 12:00 noon, while 12:00 AM represents 12:00 midnight.

Noun Shortenings for "Afternoon": aft. and aftn.

While p.m. marks specific clock times (e.g., 3:30 p.m.), writers often need to abbreviate the general noun "afternoon" in calendars, shift rosters, medical charts, or shorthand notes.

Noun Shortenings for "Afternoon":

• aft. (Standard dictionary abbreviation)
• aftn. (Common calendar / roster contraction)
• arvo (Informal Australian regional slang)

1. aft.

The abbreviation aft. is the standard dictionary-recognized shortening of the noun "afternoon." It is commonly utilized in:

• Appointment calendars: "Wed. aft. meeting"
• Academic notes and outlines: Summarizing time blocks.
• Lexicography and dictionaries: Labeling time-of-day entries.

Note: Writers must take care when using aft. in naval or nautical contexts, as "aft" is also an unabbreviated nautical term meaning toward the stern of a vessel.

2. aftn. / aftn

The contraction aftn. (or aftn without a period) removes internal vowels while preserving the consonant structure of the word. It is widely used in business, human resources scheduling, and logistics:

• Shift rosters: "Morning / Aftn / Night" shifts.
• Medical charts: Documenting symptoms occurring in the afternoon hours.

3. Regional Slang: "Arvo"

In Australian and New Zealand English, the word "afternoon" is abbreviated informally as arvo. While not used in formal writing or business contracts, "arvo" is a culturally ubiquitous colloquialism across Australia (e.g., "See you this arvo").

Formatting Rules Across Major Style Guides

Different professional style manuals enforce specific rules regarding capitalization, periods, and spacing for the afternoon time abbreviation. Adhering to the correct style manual ensures consistency across legal, journalistic, academic, and corporate publications.

The Associated Press (AP) Stylebook Rules

AP Style is the industry standard for journalism, public relations, and media publications.

• Lowercase only: Always write p.m. in small letters. Writing "2 PM" or "2 PM." violates AP guidelines.
• Include periods: Always place a period after each letter (p.m.).
• Include spacing: Always leave a space between the digit and the abbreviation (4 p.m., not 4p.m.).
• Avoid redundancy: Do not write "4 p.m. this afternoon" or "4 p.m. EST this afternoon." Write "4 p.m. today" or "4 p.m. EST."
• Noon and Midnight: AP style explicitly forbids "12 p.m." Write noon instead.

Chicago Manual of Style (CMOS) Rules

CMOS is widely used in book publishing, history, and humanities literature.

• Primary recommendation: CMOS accepts p.m. (lowercase with periods) as standard in general text.
• Alternative option: In formal typography, CMOS permits small caps without periods (PM).
• Time formatting: CMOS permits using numerals with space: 3:00 p.m.

Microsoft and Corporate Tech Style Guides

In software UI design, technical documentation, and web design:

• Uppercase PM without periods is frequently preferred for system clocks, digital displays, and user interfaces (e.g., 3:45 PM) to maximize legibility on screens.

12-Hour vs. 24-Hour (ISO 8601) Time Conventions

To avoid the potential misunderstandings inherent in 12-hour abbreviations like p.m., international standard bodies, aviation, emergency services, and the military rely on the 24-hour time system.

Time Notation Systems Comparison:

• 12-Hour System: [ 1:00 PM ] - Uses "p.m." abbreviation (Requires context)
• 24-Hour System: [ 13:00 ] - Standardized via ISO 8601 (Eliminates p.m.)

The ISO 8601 Standard

The standard maintained by the International Organization for Standardization (ISO) under ISO 8601 defines time using a 24-hour cycle (hh:mm:ss). In this system:

• Midnight is written as 00:00:00.
• Noon is written as 12:00:00.
• 1:00 p.m. becomes 13:00:00.
• 5:30 p.m. becomes 17:30:00.
• 10:00 p.m. becomes 22:00:00.

Because 24-hour notation assigns a unique integer from 00 to 23 to every hour of the day, the abbreviation p.m. is completely obsolete in international data exchange, air traffic control, maritime navigation, and global scheduling systems.

Military Time Notation

Military time is closely related to 24-hour time but omits the colon separator between hours and minutes.

• 2:15 p.m. is written as 1415 hours (pronounced "fourteen fifteen hours").
• 8:00 p.m. is written as 2000 hours (pronounced "twenty hundred hours").

Common Mistakes and Punctuation Pitfalls

When using afternoon abbreviations in written communication, several recurring mistakes degrade professionalism and visual clarity.

1. Redundant Phrasing (Tautology)

One of the most frequent errors in business and casual writing is pairing p.m. with words that already indicate the afternoon.

• Incorrect: The conference begins at 2:00 p.m. this afternoon.
• Incorrect: Please submit the report by 4 p.m. in the afternoon.
• Correct: The conference begins at 2:00 p.m. today.
• Correct: Please submit the report by 4:00 p.m.
• Correct: Please submit the report by 4 o'clock in the afternoon.

Because p.m. literally means "afternoon," combining it with "in the afternoon" is a grammatical redundancy.

2. Incorrect Period Placement and Spacing

Depending on your targeted style guide, punctuation must remain consistent throughout your document.

• Incorrect spacing: 3:00p.m. (Missing space after numerals)
• Inconsistent periods: 3:00 p.m or 3:00 pm. (Missing internal or terminal periods)
• Mixed cases: 3:00 Pm or 3:00 p.M. (Incorrect capitalization)

3. Combining "o'clock" with p.m.

The term "o'clock" (a contraction of "of the clock") should never be paired directly with p.m. or a.m.

• Incorrect: We will meet at 3 o'clock p.m.
• Correct: We will meet at 3 p.m.
• Correct: We will meet at 3 o'clock in the afternoon.

4. Sentence-Ending Punctuation with p.m.

When an abbreviation ending with a period appears at the very end of a declarative sentence, do not add a second period.

• Incorrect: The meeting finished at 4:30 p.m..
• Correct: The meeting finished at 4:30 p.m.
• Exception (Questions/Exclamations): If the sentence is a question or an exclamation, place the question mark or exclamation mark immediately after the final period: Did the meeting finish at 4:30 p.m.?

How to Abbreviate Afternoon in Formal, Legal, and Business Contexts

Depending on your professional field, specific conventions dictate how you present time data.

1. Legal Contracts and Formal Invitations

In formal legal documents, property deeds, and formal event invitations, times are often written out in full words to prevent ambiguity or fraudulent alteration of numerical digits.

• Legal text example: "This agreement shall take effect at four o'clock in the afternoon (4:00 p.m.) Eastern Standard Time..."
• Invitation example: "Requests the pleasure of your company at four o'clock in the afternoon..."

2. Medical and Health Records

Healthcare professionals use specialized shorthand to record medication administration times and patient observations. Guidelines from national health organizations encourage clear documentation:

• Q.D. / QPM: "Every afternoon" or "every evening" (from Latin quaque die post meridiem). However, many medical systems encourage writing out "daily in the afternoon" to prevent clinical errors resulting from misread Latin abbreviations.

3. Business Rosters and Spreadsheets

In administrative scheduling, human resources databases, and column headers where space is strictly constrained:

• Use Aft or Aftn for shift column headers (e.g., Shift A: Morn | Shift B: Aft | Shift C: Night).
• Ensure standardized cell formatting in software like Microsoft Excel or Google Sheets by selecting explicit hh:mm AM/PM or 24-hour time settings.

Frequently Asked Questions

What does p.m. stand for when referring to the afternoon?

p.m. stands for the Latin phrase post meridiem, which translates to "after midday." It designates all clock times from 12:00:01 noon until 11:59:59 at night.

What is the noun abbreviation for afternoon?

The standard lexicographical abbreviation for the noun "afternoon" is aft. another widely accepted written contraction is aftn. (commonly used in administrative calendars and shift rosters).

Is 12:00 PM noon or midnight?

12:00 PM represents 12:00 noon on modern digital clocks, standard timekeeping devices, and digital systems. However, because post meridiem means after noon, exact 12:00 solar noon is technically neither a.m. nor p.m. To avoid legal or operational confusion, major style guides recommend writing 12 noon instead of 12:00 p.m.

Should p.m. be capitalized or lowercase?

Capitalization depends on your chosen style guide. AP Style and APA Style require lowercase with periods (p.m.). The Chicago Manual of Style accepts lowercase with periods (p.m.) or small caps (PM). Many modern digital interfaces use uppercase without periods (PM). The key requirement is consistent usage throughout your document.

How do you punctuate p.m. at the end of a sentence?

If a sentence ends with p.m., the period in the abbreviation serves as the sentence-ending period. Do not add a double period (p.m..). If the sentence is a question or exclamation, add the punctuation mark directly after the final period (p.m.? or p.m.!).

Final Summary and Next Actions

To maintain clear and accurate communication in all written work, follow these core principles:

1. Use p.m. for specific times: Match your formatting (p.m. vs. PM) to your required style guide (AP, Chicago, APA, or corporate brand guidelines).
2. Use aft. or aftn. for noun shorthand: Reserve these abbreviations for calendars, scheduling spreadsheets, and informal note-taking where space is limited.
3. Eliminate redundancy: Avoid writing "p.m. in the afternoon" or "3 o'clock p.m."
4. Clarify midday: Use 12 noon or 12 midnight in legal, contractual, and technical documentation to avoid ambiguity.
5. Consider 24-hour time: For international scheduling, transport, or aviation, adopt 24-hour time notation (ISO 8601) to remove AM/PM distinctions altogether.