Project for the Web start and end times

We have a business requirement to set start and end times (or could be start time and duration) for tasks.  During a go-live, we plan tasks to the 15 minute increment.  For example, we need to specify that Task1 starts at 9:00, Task 2 at 9:15, Task 3 at 9:30, task 4 at 10:15, etc.  I feel like there should be Start/End DateTime field types, but cannot find such a thing.

Thoughts?