Durations as Whole Working Days
Why shouldn't I use hours and minutes in my duration values? Sometimes I have tasks that take very little time out of the day and I don't want them calculating a whole day's worth of resources.
Duration is the time period within which the work will be performed, not a measurement of the amount of work. A ten-day duration task may only have 12 hours of work being performed by a 40 hour/week resource during the course of the 10 days. It's very difficult within most projects for a project manager to be so specific as to designate the specific hour and minute within which the work for a task owner will be performed.
Even if a task can be defined down to the very hour and minute of occurrence, predecessor and successor relationships are difficult to adjust on a dateline view if duration settings push a two-day task into a third day because of a one-hour predecessor that may be very difficult to see on a Gantt chart. Even more difficulties may be experienced if you have to locate hours and minutes inside of lead and lag time durations for predecessors.
How do I schedule tasks with predecessor/successor relationships that must occur on the same day because they are short duration tasks, without using hour and minute durations?
Make these tasks whole day tasks and use a one-day lead time in the predecessor settings. You will still maintain the appropriate relationships in terms of the predecessor/successor values, but the tasks will show on the Gantt chart as overlapping tasks to occur on the same day. Auto-alerts for predecessor completions will work the same as they would if you had used hours and minutes without the one-day lead time setting.