Playground

Every endpoint, live, no key. Pick one, set the inputs, and read the response the API would give you. A few dozen calls a day are free here; after that, a key takes thirty seconds.

Endpoint

Region

Date

Terms

net30 from Jan 15, 2027 crosses a weekend and a federal holiday.

Pick an endpoint and press Run.

From playground to production

The equivalent production call is the request line above with your key attached:

curl "https://dierum.io/v1/due-date?region=US&invoice_date=2027-01-15&terms=net30" \
  -H "X-Api-Key: $KEY"

The reference has the same examples in Python, JavaScript, and C#, plus recipes for invoicing, SLAs, payroll, and settlement.