Use case · For payroll software and payroll providers

Calculate a prorated salary by working days when someone joins or leaves

When someone joins or leaves mid-month, count the working days by state and prorate the salary.

To prorate a salary by working days, divide the working days in the partial month by those in the full month. Example: someone starts in Hesse on January 15, 2027. Up to January 31, 2027, that makes 11 working days. The method is not set by law. The employment contract or collective agreement has to provide for it.

Pass the start or leaving date and the state of the place of work.

Fetch the working days in the partial month and in the full month with hr_arbeitstage.

Prorate the salary in proportion to the working days, if the contract or collective agreement provides for this method.

Three methods, and the contract decides

There are three common ways to calculate a partial month: by calendar days, by 30 days per month or by working days. The employment contract or collective agreement (Tarifvertrag) decides which one applies, not the law. The working days method is precise, but it needs the public holidays at the place of work.

That is exactly what the working days calculator counts: Monday to Friday, minus the state's public holidays, and regional ones too if you want.

How to calculate

Query the working days from the start date to the end of the month, or for a leaver from the first of the month to the last working day.
Query the working days of the full month.
Monthly salary times working days in the partial month, divided by working days in the month.

The calculator only counts Saturdays if you pass samstag=true, for example for a six-day week.

What the call looks like

Example with the dataset Working days calculator. The response comes from the same code as the API.

api.quellenkontor.dev/v1/hr/arbeitstage?von=2027-01-15&bis=2027-01-31&land=HE

Zur API-Doku →

curl "https://api.quellenkontor.dev/v1/hr/arbeitstage?von=2027-01-15&bis=2027-01-31&land=HE" \
  -H "Authorization: Bearer $QK_KEY"

import { Quellenkontor } from "@quellenkontor/sdk";

const qk = new Quellenkontor(process.env.QK_KEY);
const daten = await qk.hr.arbeitstage({ von: "2027-01-15", bis: "2027-01-31", land: "HE" });

import os
from quellenkontor import Quellenkontor

qk = Quellenkontor(api_key=os.environ["QK_KEY"])
daten = qk.hr.arbeitstage(von="2027-01-15", bis="2027-01-31", land="HE")

$ qk arbeitstage --von 2027-01-15 --bis 2027-01-31 --land HE

{
  "name": "hr_arbeitstage",
  "arguments": {
    "von": "2027-01-15",
    "bis": "2027-01-31",
    "land": "HE"
  }
}

This is how an agent calls the tool. Server setup is described in the MCP docs.

Antwort200 OK · JSON

{
  "datensatz": "arbeitstage",
  "von": "2027-01-15",
  "bis": "2027-01-31",
  "land": "HE",
  "land_name": "Hessen",
  "samstag_als_arbeitstag": false,
  "regionale_feiertage_abgezogen": false,
  "kalendertage": 17,
  "arbeitstage": 11,
  "feiertage_an_arbeitstagen": [],
  "rechtsgrundlage": "Hessisches Feiertagsgesetz (HFeiertagsG), Hessen",
  "quelle": {
    "titel": "Hessisches Feiertagsgesetz (HFeiertagsG), Hessen",
    "url": "https://www.rv.hessenrecht.hessen.de/bshe/document/jlr-FeiertGHE1952pP1"
  },
  "quellen": [
    {
      "titel": "Hessisches Feiertagsgesetz (HFeiertagsG), Hessen",
      "url": "https://www.rv.hessenrecht.hessen.de/bshe/document/jlr-FeiertGHE1952pP1"
    }
  ],
  "hinweise": [
    "Gezählt werden Montag bis Freitag.",
    "Regionale Feiertage sind nicht abgezogen. Setze regionale=true, wenn dein Standort in einem Gebiet mit regionalem Feiertag liegt."
  ],
  "stand": "2026-09-23",
  "lizenz": "Berechnung nach den genannten Normen. Nutzung nach den Nutzungsbedingungen von Quellenkontor.",
  "zitat": "Arbeitstage vom 15.01.2027 bis 31.01.2027 in Hessen: 11 von 17 Kalendertagen, Montag bis Freitag ohne gesetzliche Feiertage des Landes. Rechtsgrundlage: Hessisches Feiertagsgesetz (HFeiertagsG), Hessen. Quelle: Hessisches Feiertagsgesetz (HFeiertagsG), Hessen, https://www.rv.hessenrecht.hessen.de/bshe/document/jlr-FeiertGHE1952pP1. Daten: Quellenkontor (quellenkontor.dev).",
  "datenstand": "2026-09-23.1"
}