Imports name this capability’s declared dependencies, which fune builds next to it in your project; each one links to its page.
from .dates_add_days import days_in_month, format_iso_date, parse_iso_date, CivilDate ← from dates.add-days ^1.0.0 · built alongside by fune
from .dates_month_boundaries_types import MonthBoundaries
def month_boundaries(iso: str) -> MonthBoundaries:
"""The first and last day of the month containing a date, and its length.
All three are returned together because a caller needs them together - a
billing period, a statement range, a pro-rata fraction - and because
deriving ``end`` from ``start`` in caller code is where "31 January plus one
month" bugs come from.
``end`` is the last day of the month, inclusive, not the 1st of the next
month. Inclusive is what a statement prints and what a human checks against.
"""
date = parse_iso_date(iso)
# February is the only month whose length is not a constant, and it follows
# the full Gregorian rule: 2024 had 29 days, 1900 had 28 (a century year),
# 2000 had 29 (divisible by 400).
days = days_in_month(date.year, date.month)
return MonthBoundaries(
start=format_iso_date(CivilDate(date.year, date.month, 1)),
end=format_iso_date(CivilDate(date.year, date.month, days)),
days=days,
)
def is_month_end(iso: str) -> bool:
"""True when the date is the last day of its month - a common billing trigger."""
date = parse_iso_date(iso)
return date.day == days_in_month(date.year, date.month)