Clarity does not ever create timesheets.
Users create timesheets when they click on the icon in their timesheet screen.
Clarity might expect a user to create a timesheet though, and report on that in various places.
There are various solutions to control this ; e.g. submit time against a holiday project / users set their personal calendars as non-working days / closing resources for time-entry whilst they are on holiday.
There is no simple answer though; how is best to do this for your organisation will depend upon your organisation - perhaps the easiest option is to just ignore it!