Timesheets - should not be able to add more than 24hrs in a day

There is field level validation in Timesheet entry that will give an error if a value greater than 24 is entered. "Value is not in correct format"

you can add in a validation rule here is mine for help (GetSumOfTimesheetReportHoursForGivenPeriod($reportedby, $ReportedDate,$ReportedDate) + $duration )> hours(24)

But agreed should be standard out the box