Number and time conventions

Overview

Using clean, consistent number and time formatting improves readability, reduces confusion, and creates a polished, user-friendly web experience.

Numerals vs. numbers

Reference the following guidance to understand when to use numerals and when to use numbers.

• Spell out one through nine, except in percentages and hard data. Use Arabic numerals for 10 and above. For numbers in the millions use the numeral and spell out million (e.g., 2 million). The same rule also applies to ordinals (second vs. 15th).
• Example: I have nine shirts. I have 12 shirts.
• Spell out numbers used at the beginning of a sentence. Exception: Never spell out years.
  
• Always use numerals for ages. If the age is used as an adjective, it should be hyphenated.
• Example: She has a 1-year-old girl. Her daughter is 1 year old.
• Example: The boy was 7 years old.

Currency

The following guidance details when to use the word “dollar” and when to use a $ sign.

• Use the dollar sign when speaking of a specific amount and always use numerals.
• Example: Gene owes me $5.
• Write out “dollar” when speaking metaphorically.
  
• Example: He doesn’t have a dollar to his name.

Percentages

Spell out the word “percent” unless there are space constraints.

• Example: His tumors shrank by 75 percent.

Phone numbers

Follow this guidance to ensure consistent, industry standard formats.

• Use hyphens (dashes), not periods or parentheses, to separate phone numbers. Use the area code with all phone numbers.
• If content is meant for foreign audiences, use proper country code.
• Do not use "1" before any phone numbers, including 800-789-7366.
• When using a phone number commonly published with letters, use the numerals with the letters in parentheses. (e.g., 888-544-4636 (LGH-INFO))

Temperature

Refer to this guidance when content includes temperature information.

• Use numerals for all except zero. Spell out “degree”.
• If it’s necessary to use Fahrenheit, use 10 degrees Fahrenheit, or 10 F if degrees and Fahrenheit are already clear in context.
• The degree circle symbol is never used.
• Use a word, not a minus sign, to indicate temperatures below zero.
• Example: The low was 10 degrees below zero.
• Temperatures are higher or lower, not warmer or cooler.
• Example: Her temperature was 5 degrees higher than expected.

Time

Ensure consistent presentation of time information by following this guidance.

• Use numerals except for noon and midnight.
• Do not capitalize and use periods when writing a.m. and p.m.
• Add a space between the numbers and a.m. and p.m. (e.g., 5:30 p.m.).
• Don’t use :00 with times. (6 a.m. not 6:00 a.m.)
• Don’t include morning, afternoon or evening when using a.m. or p.m.
• Start time and end time are separated by “to” not a hyphen or dash.
• If a span of time is within the morning or afternoon, only one time marker is used.
• Correct Example: 9 to 11 a.m.
• Incorrect: 9 a.m. to 11 a.m.
• Write “24 hours a day” as shown; not hyphenated.

Day and date conventions

Although not obviously a number, day and date information also has standard formats that should be followed.

• All days should be spelled out (e.g., Monday, Tuesday) except in tabular form where they can be abbreviated to their first three letters (e.g., Mon, Tue, Wed, Thu, Fri).
• Use numerals with dates and do not use st, nd, rd, or th (June 1, not June 1st) unless part of specific name (e.g., 1st Ward)
• Spell out the month unless it is used with a date. When used with a date, abbreviate only the following months: Jan., Feb., Aug., Sept., Oct., Nov. and Dec.
• When a phrase lists only a month and year, spell out the month and do not separate the month and the year with commas. (January 2023)
• When a phrase refers to a month, day and year, set off the year with commas (Jan. 2, 2023).
• Do not use “on” before a day or date.
• Correct example: The group met Tuesday, March 5.  
• Incorrect: The group met on Tuesday, March 5.
• For decades, either 1960s or ‘60s. Do not use apostrophes between the number and the s.
• To keep content evergreen, avoid referring to past events as “last year” or “XX years ago”. Instead, use the year the event occurred, if known.
• Correct Example: In 2021, he went on vacation.
• Incorrect: Last year, he went on vacation.

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