Calculate business days in Python

Add or count working days with numpy, the holidays package, or the Dierum API.

Option 1: numpy

numpy.busday_offset and numpy.busday_count handle business-day arithmetic. By default they skip Saturday and Sunday only; pass holidays explicitly.

import numpy as np

np.busday_offset("2027-03-25", 2, roll="forward")
# numpy.datetime64('2027-03-29')  (Sat/Sun skipped, Good Friday not)

np.busday_offset("2027-03-25", 2, roll="forward",
                 holidays=["2027-03-26"])
# numpy.datetime64('2027-03-30')

The weekmask parameter supports non-standard weekends, e.g. weekmask="Sun Mon Tue Wed Thu" for Saudi Arabia.

Option 2: the holidays package

pip install holidays. Gives you the holiday dates; combine with numpy or your own loop for the arithmetic.

import holidays

us = holidays.country_holidays("US", years=2027)
"2027-11-25" in us          # True
us.get("2027-11-25")        # 'Thanksgiving'

Option 3: Dierum API

One request; holidays, subdivision calendars, market calendars, and per-country weekends are maintained server-side.

import requests

r = requests.get(
    "https://dierum.io/v1/add",
    params={"region": "XNYS", "start": "2027-03-25", "days": 2},
    headers={"X-Api-Key": KEY},
)
r.raise_for_status()
r.json()["result"]          # '2027-03-30'

Region codes cover countries (US), subdivisions (US-CA, DE-BY), and financial markets (XNYS). See the API reference for counting, due dates, and pay schedules.