Scenario:
A validation rule is setup which specifies that a user cannot submit the timesheet if the total hours is less than forty for a week. The validation rule is assigned to the users on their profile. However, a user is able to submit the timesheet with less 40 hours. The timesheets have been deleted and re-created, yet the validation rule is not affecting the timesheet.

Cause:
If the user's Start date, is a day after the start date of the timesheet period, then the validation rule will not be applied for that particular timesheet period,

Resolution:
No changes have to be made in the user's profile, user's timesheet or in any settings of the Web TimeSheet. The Validation rule would come into effect automatically from the next timesheet period.