Dates & Time
You’d think that something as basic as stating a date or a time wouldn’t require its own set of rules. But when it comes to writing out dates and times, you actually have more options than you probably realize. Follow these guidelines to make sure your dates and times are consistent with one another.
Rules for Dates and Time
Days
If space allows, write out the full name of each day of the week (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday).
When space is limited, use the three-letter abbreviation without a period (Mon, Tue, Wed, Thu, Fri, Sat, Sun).
Months
If space allows, write out the full name of each month (January, February, March, April, May, June, July, August, September, October, November, December). When space is limited, use the three-letter abbreviation without a period (Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec).
Years
Though a number generally shouldn’t be used to start a sentence, it is acceptable to start a sentence with a year.
1999 was a crazy year.
Use the abbreviations AD and BC only if the date may be otherwise unclear. AD and BC should be placed in uppercase letters after the year, without periods.
He ruled from 10 BC to 20 AD.
Decades and Centuries
To write a decade, add a lowercase "s" without an apostrophe (the 1820s). To abbreviate a decade, replace the first two digits with an apostrophe, but do not add an aposotrophe after the number (the ‘80s).
To write a century, use numerals for the ordinal even for centuries with single digits (8th century, 21st century).
Dates
When writing a date, if space allows, use the full or abbreviated name of the month without ordinals (such as 1st or 2nd).
- December 6, 2009
- Mar 17, 2012
- August 7
When it’s necessary to use numerals for the full date, always use slashes, and avoid the use of leading zeros:
- 8/7/78
- 11/16/2012
When a date consists of only a month and year, don’t separate the two with a comma.
March 2011 was unseasonably warm.
When stating the month, day, and year in a sentence, put a comma after the day.
Her May 20, 2012 birthday party was a success.
Days and Dates
When stating a day and date together, put a comma after the day and follow the above-listed guidelines.
The meeting is scheduled for Thursday, Nov 15, 2012.
Time
Use numerals to state all times except noon and midnight, which should be written out.
Ante and post meridian should be abbreviated with lowercase letters, without periods, and without a space between the number and the am/pm (9am, 4pm).
On-the-hour times do not need to include the minutes unless other times in a range or sentence have a minute specification. Time ranges should be separated by a dash (“ - “) with one space on each side.
- Our store hours are 10:00am - 5:30pm.
- We open daily at 8am.
Time Zones
Time zones should be abbreviated to two letters (PT, ET, MT, CT), unless there is a specific reason to indicate daylight versus standard time. There should be a space between the time and the time zone abbreviation.
Let’s set up a conference call for 5pm ET.