When arriving at a job you can track your work time right in the mobile app using 'Timesheets'.

Click on the 'plus sign'

Click on the plus sign beside the Timesheets. This allows you to enter the start and end time. You can also manually enter time with or without a job assignment by tapping the + plus sign and click on Save once done and the time will be added to the job.

To view your timesheets for the week/day, select the Timesheets link in the daily or weekly views, accordingly.

Once work is completed on the job you can update the status. If you need to revisit the job, it might be better to change the status to 'Incomplete'.

You can then go back to the job and use Actual Timesheet feature again to track your time for another visit. Check out this article on managing multiple visits for the same job.