Ordinal Numbers in Dates
Many professional house styles omit ordinal suffixes when a full calendar date includes a month. Microsoft says not to use ordinal numbers such as “1st” or “23rd” for dates, and the Australian Government Style Manual likewise prefers forms such as “27 December.”
In styles such as Microsoft and the Australian Government Style Manual, write the day as a cardinal numeral in full dates—“27 December,” not “27th December.”
Key details
Important caveats
Exception Boundary
The Australian Government Style Manual allows an ordinal when the day is referred to without the month, such as “by the 20th”; do not turn the full-date convention into a universal ban on ordinals.
Further guidance
Full Date Rule
For the cited house styles, omit ordinal suffixes when the month is present.
Practical Application
When a full date includes the month under the cited Microsoft or Australian Government conventions, write the day as a cardinal numeral: “27 December” or the house-style equivalent, not “27th December.” Preserve ordinal forms when the governing style allows them in a different construction, such as referring to a day without the month.
Reader Check
Is this a full calendar date with a month, and which house style controls the document? Do not turn one style’s convention into a universal grammar rule.
Worked Example
Full date: “The meeting is on 27 December.” Separate day reference where the governing style permits it: “Please reply by the 20th.”
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Dates and time — Australian Government Style Manual (opens in a new tab)Australian Government Style Manual · Australian Government guidance for day–month–year dates, ordinal dates, decades, centuries, time zones, and en-dash spacing in date/time spans
- Date and time terms — Microsoft Style Guide (opens in a new tab)Microsoft · Official Microsoft house-style guidance for dates and times, including date ordering and formatting examples.