I have not tested this in OpenOffice, but it should work just the same

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So the purpose of this is to track four categories of time.

• Working Time
• Working Overtime
• Travel Time
• Travel Overtime

Working Time and Travel Time never exceed 8 hours. Any work or travel performed beyond 8 hours must be entered as overtime. Work and Travel on Saturday and Sunday is always entered as overtime

This scenario requires that work starts after 00:00 and ends before 24:00. All the calculations require the time to be entered in 24 Hour time.