Work log timer helps you to determine the amount of time spent for a work more precisely. You can hide and show issue timer any time you want. When it is visible it remains on the bottom right hand side of the page and shows active issue and how much time passed since it is started. When you press the stop button, "Work Log Dialog" is opened. Issue, time spent, and start date fields are pre-populated from the timer but you can made any adjustment you want on the dialog before actually submitting the work log.
You can view list of all timers for the issues matching a JQL using 'Timer Dashboard Item' if you have permission to view issues.
Once started for an issue, it will continue to count even though you browse other issues or pages or even when it is hidden, until it is stopped. You can't start another timer for another issue until you stop the current one because it is not possible to work on more than one issue at a time.
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