When working with translation jobs, you can use time tracking functionalities, both on job level and individual job tasks level. On the screenshot below, you can see that Work time field exists on a job level, and for each individual task existing in a job:
When you specify work time for individual task, application automatically summarizes work time from all job tasks and fills job's work time automatically. Additionally, if current unit of a task is time, then recorded time will be automatically converted into hours and recorded to the Quantity field.
Each Work time field has Start and Stop buttons, which allow to automatically record your work time. However, you have to remember to click Stop button when needed. When timer is enabled and job task unit is time, you can see how quantity grows in real time.