Today, there is an app, website, or software platform for just about anything (including finding someone to walk your dog).
But when it comes to time measuring, there is 1 app I can't live without:
TimeCamp
And here's why:
Reason #1: measures the time automatically and runs in the background
Reason #2: readable timesheet allows easy corrections to be made
Reason #3: you control the assignment of time to relevant projects by using keywords
Reason #4: allows you to measure your productivity
Reason #5: allows you to create invoices and report working time
If you want to effortlessly measure your time, measure your productivity, or find out where your time goes, I can't recommend using this app enough.