This is caused if the Timesheet period setup is monthly, or if the Timesheet period type setup in the users profile in wrong. We request you to check in the users profile as shown in the screenshot as too what is the timesheet period setup:-
Eg., in the above screenshot Timesheet period type is Employee type. Check under Administration > Timesheet Periods to see if any Timesheet Period's are created for Employee Type.
As per the above screenshot this may be one of the reasons why Timesheets may be getting created from 1st Nov, as the effective date for the Timesheet Period is from 1st Nov.