All of the date fields in Project are actually date/time fields and you can
enter duration in your choice of units down to the minute level. Tasks are
always physical activities and they take place at specific points in time -
you might not know what those points are ahead of time but none the less,
when they occur is always going to be some precise and observable date and
time. If I'm being accurate enough to schedule resources to show up to do
the work I can't just say it will take 2 hours or even that I'm going to
wash the car at 3pm - I need to say I'll start washing it Saturday
afternoon, the 9th of April 2005, at 3pm, a precisely defined instant in
time, and it will take 2 hours to complete.
