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.
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 · Microsoft house style for AM/PM and human-facing time notation