I've just played with Libre Calc and it seems all you need to do is set the cell format to time as hh:mm then subtract start time from end and sum the total time cells. Calc appears to take care of passing midnight events.
See http://superuser.com/questions/387106/li...mmss-cells for the format for the total hours cell
See http://superuser.com/questions/387106/li...mmss-cells for the format for the total hours cell
1) Lenovo T520 i5 LL3.8 8GB ram, fast & stable
2) Medion P4 32bit LL3.8 1GB ram, quite fast & stable
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2) Medion P4 32bit LL3.8 1GB ram, quite fast & stable
3) eeePC 901 32bit LL3.8 1GB ram, fast & stable
4) eeePC 701 32bit LL3.8 1GB ram, slower & stable but small and light enough to travel with me to New Zealand when visiting family in Blenheim.