Reference · Dates

date.end_of_month

date.end_of_month(str) -> str

What it does

The last day of a date's month, as ISO text: the 28th, 29th, 30th or 31st, the leap year taken into account. It takes a date, not a date-time.

Examples

print(date.end_of_month("2026-10-27"), date.end_of_month("2026-04-01"))print(date.end_of_month("2026-02-10"), date.end_of_month("2024-02-10"))

2026-10-31 2026-04-302026-02-28 2024-02-29

Edge cases

• The last day of a month gives itself.
• The day after it is the start of the next month, so date.add_days(end, 1) is a way to the first of next month too.

print(date.end_of_month("2026-10-31"))print(date.end_of_month("2026-10-27") | date.add_days(1))

2026-10-312026-11-01

Errors

A date-time, text that is not a date, or any other value is a runtime error, not an error value.

print(date.end_of_month("27/10/2026"))

line 1: `date.end_of_month` expects a date (YYYY-MM-DD) as argument 1, got "27/10/2026"

Chaining

print("2026-10-27" | date.end_of_month | date.format("dddd D MMMM"))print(range(1, 13) | map((m) => date.of(2026, m, 1) | date.end_of_month | date.parts | (p) => p.day))

Saturday 31 October[31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

See also

date.start_of_month, date.days_in_month, date.add_months, date.is_leap_year

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