The National Math + Science Initiative implemented a time tracking system for all employees that made it difficult  to enter time as you worked. To track time throughout the day/week I created a paper timesheet in Adobe Illustrator. It is similar to one I had used early in my career with a few improvements.

It tracks a 24 hour day. Most timesheets will track a 10-12 hour day usually 6am to 6pm. As an IT person that does a significant amount of work after hours, while systems are less utilized, I was having to use multiple lines and write extra notes to know where the time had really been spent.

Hours are broken into 15 minute increments.  In my experience trying to track time beyond chunks of 15 minutes wastes more time than it saves. Also getting too granular in what you are tracking can be a terrible burden on the employee and on the person trying to bill their time out. As long as the assigned tasks are being accomplished and the time spent matches up at a high enough level to be billable/accountable then going further shouldn't be necessary.  The quarter hour seems to be the sweet spot between insane and billable.

One task equals one line.  My days are usually spent jumping from one task/project to the next. As I have to start and stop I can record everything for that on a single line (see my example below).

View days and weeks in one place.  As you start to fill in the sheet you start to get a visual sense of where time is spent and how much jumping around you are doing. I put enough Project/Task lines in so that most folks can see an entire week in one or two pages.