The key date is overwritten with the date from the change number record

What causes this issue?

You are attempting to create, change or display a routing with a change
number.
The default value for the key date is the current date. When you enter
achange number, the current date will be overwritten by the date from
the change number.

System Response

When you create a routing, the system enters the new data records for
this date.
When you create a routing with a history, the changes for this date are
valid.
When you select or display a routing, only the routings that are valid
for this key date are selected.

Error message extract from SAP system. Copyright SAP SE.