A date the calendar does not have
impossible-dateon by defaultJapanese / English
A date not on the calendar ("February 30"), or a year two calendars disagree on
Example
How to fix
Check the date that was meant and correct it. For the end of a month, write that month's last day (30 April, 28 February).
Why it matters
A date such as "February 30", "April 31" or "2023-02-29" is not on the calendar. The reader has to find out whether the day before, the day after or another month was meant, and for a deadline someone acts on the wrong day. It happens when the end of a month is taken to be the 31st, or a leap-year schedule is reused. When a Japanese era year and the Western year in brackets beside it disagree (令和6年（2023年）, where 令和6 is 2024), the reader cannot tell which year is meant. Month lengths, leap years and the first year of an era are fixed by the calendar, so a machine can tell.
What it does not flag
For a year in a Japanese era, and for a date without a year, February 29 is not reported, since the leap year cannot be decided. A bare run of numbers such as 2026-13-45 may be an identifier or a version, so it is compared with the month's length only when the month is 1 to 12 and the day at most 31; a date with a month's name is likewise checked only up to the 31st. An era year and a Western year in brackets are compared only as calendar years; a fiscal year (令和6年度（2023年度）) and an era whose first year the lexicon does not give are not read. Code is not read.
Turning it off or relaxing it
Technical details
- Layer
- L3
- Status
- stable
- Severity
- error
- Languages
- Japanese and English
- Suited to
- business, technical, blog, legal, docs, academic, literature, speech
- Reads from the document
- dates
Levels
Set a level for this rule under rules in chaff.yaml. With nothing set, it runs at the level its genre gives it (see By genre below).
| normal | error |
|---|---|
| relaxed | warning |
This rule has no limit to count to. A level sets how a finding is marked: relaxed keeps the finding and marks it a step lower.
By genre
- Runs by default in
- technical/spec, technical/readme, blog/tech, blog/essay, blog/owned-media, business/proposal, business/report, business/email, business/press-release, business/meeting-notes, legal/contract, legal/statute, legal/judgment, legal/patent, docs/manual, docs/faq, docs/glossary, academic/paper, literature/fiction, literature/essay, literature/poetry, literature/play, speech/address, speech/transcript
Message
"{written}" is not on the calendar (that month has {days} days)
"{written}" is not on the calendar (that month has {days} days)
"{written}" is not on the calendar (that year is not a leap year, so February has {days} days)
"{written}" is not on the calendar (months run from 1 to 12)
"{written}" names two different years (outside the brackets {year}, inside {glossYear})
Rewrite depth (chaff fix-plan --depth): light — words and sentences; the structure and the voice stay
This page is built from the rule's definition file:packages/chaff/rules/impossible-date.yaml