Factory calendar ID & does not exist or is not active

What causes this issue?

The entry in plant table T001W contains a factory calendar ID for which
no active calendar could be found.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Change the factory calendar ID in table T001W or define and load a
calendar with the ID already specified there.

Error message extract from SAP system. Copyright SAP SE.