And what problem does that cause for you?
a) Is the file hosted from FileMaker Server?
b) What does the script do?
If hosted from server you can set up a server schedule. But not all script steps are server side compatible. Other operations, such as import/export are severely limited.
Scripts can also be scheduled to run when the file is not hosted by server and can be set up to run from a "client context" when it has steps that are not server compatible.