This is specifically what I have been working on this week. I thought I had all the bugs gone, but new ones popped up. I added the Activity to this and the Summary Display [link] so that what they are doing can be reviewed.

The drop down box contains all the names of all the students. When you select a different name, the current student's data is saved.
If the new student has already done something today, it will bring it up to show you.
If not, then it will take the end time from the last student and put it in the start time. That way, the new student can begin their time as soon as the old student finishes.

The Today button puts today's date in, and it can be changed as necessary. Likewise with the now buttons and the current time. The activity will carry over to the next student because they will all likely be doing the same thing.

All this data goes into their file for reports later. This is what comes up when you choose Student -> PE Time.