datefun

Functional approach to date manipulations

Date is string. In ISO format (Y-M-D). Mostly it came from database.

Now we want some manipulations and return again ISO date as string.

Conversion functions:

• dt_make(year: int, month: int, day: int) -> str
• dt_from_object(obj: datetime) -> str

Date (string) output functions:

• dt_month_start(iso_date: str) -> str
• dt_month_end(iso_date: str) -> str
• dt_week_start(iso_date: str, week_start_monday: bool = True) -> str
• dt_week_end(iso_date: str, week_start_monday: bool = True) -> str
• dt_quarter_start(iso_date: str) -> str
• dt_quarter_end(iso_date: str) -> str
• dt_semiyear_start(iso_date: str) -> str
• dt_semiyear_end(iso_date: str) -> str
• dt_year_start(iso_date: str) -> str
• dt_year_end(iso_date: str) -> str
• dt_add_years(iso_date: str, many_years: int, interpret_0228_as_monthend: bool = True) -> str
• dt_add_months(iso_date: str, many_months: int, stay_in_month_end: bool = True) -> str
• dt_add_days(iso_date: str, many_days: int) -> str
• dt_easter(year: int) -> str
• dt_easter_gauss(year: int) -> str
• dt_good_friday(year: int) -> str
• dt_pentecost(year: int) -> str
• dt_add_week(iso_date: str, many_weeks: int) -> str
• dt_add_quarter(iso_date: str, many_quarters: int, stay_in_month_end: bool = True) -> str
• dt_add_semiyear(iso_date: str, many_semiyear: int, stay_in_month_end: bool = True) -> str

Boolean output functions:

• is_leap_year(year_or_date: int | str) -> bool
• is_valid_date(iso_date: str) -> bool

Integer output functions:

• int_days_in_month(iso_date: str) -> int

No external dependecies (only internals, eg. datetime)

Needs python 3.10 (because of type hints/annotations with pipes)

install

pip install datefun

(or pip3 or pipx)

usage

from datefun import datefun

print(datefun.dt_add_months("2025-02-28", -1)) # outputs 2025-01-31
print(datefun.dt_add_months("2025-02-28", 1, False)) # outputs 2025-03-28

or

from datefun.datefun import dt_add_months

print(dt_add_months("2025-02-28", -1)) # outputs 2025-01-31
print(dt_add_months("2025-02-28", 1, False)) # outputs 2025-03-28