I am working on a timesheet in Excel and seem to have come upon a strange
quirk/error. The timesheet is supposed to take two times, find the difference
and then display it in decimal format.

For example:
A1 = 09:00
A2 = 09:30
A3 = 0.5

The formula I have in cell A3 for making this computation is:

ROUNDUP((A2-A1)*1440/60,1)

The idea of the roundup is so that as soon as you work more than a specific
tenth of an hour you get credit for the next tenth. The breakdown of an hour
would be as follows:

..1 = 1-6 minutes
..2 = 7-12
..3 = 13-18
..4 = 19-24
..5 = 25-30
..6 = 31-36
..7 = 37-42
..8 = 43-48
..9 = 49-54
1.0 = 55-60

The issue I am having occurs for time differences of 30 minutes but only at
specific times. One of these ranges for example is 14:30 to 15:00. When the
formula calculates the time difference it comes out incorrectly to just over
..5 so it is rounded up to .6.

Does anyone have any ideas on how to workaround this or why Excel does this?

Thanks,
The Merg
--
Today's problems don't worry me,
I haven't solved yesterday's yet.