Gerard's answer is how to accomplish it, but with respect to the 24 hour
calendar I suggest you think it thru to make sure it really should apply.
The 24 hour calendar says that work on the tasks proceeds 24/7. It also
implies that once a task begins it doesn't "stand down" until it's
completed - the resources go 24/7 and don't sleep, eat, nap, see their
families, or do anything but work for how ever long it takes to finish the
task. Machines may work like that but people don't. If you have a painter
assigned to pain a room and it's going to take him 6 days to do it, he'll
probably go home in the evenings as it progresses. The 24 hour calendar
suggests that he'll work 48 hours solid until the painting is done, not very
likely.