I dont really get how time tracking work since it adds up all estimation?

[Ahmed Alghamdi]

So, picture with me there is one user story. and we have let's say three developers, each one of them has created one sub-task for that user story to complete. Let's say that each one of them has estimated that it will take one day to complete their his/her task. 

in the above scenario, and according to Jira setting, once you do the above, it will tell you that the user story in question requires 3 days to complete!!! where in fact it should take only one day since we have 3 developers and each will work on their own and would consume one day to finish!! that is what i dont get.

same issue above appears when i make a sprint, we drag all the user stories along with their sub-tasks. we have a four week sprint and we have allocated real estimation for the four weeks, but all the sudden because JIRA adds up all time it suggests that the remaining work to be done is something like hundred of weeks!!!?

Many thanks

[Nic Brough -Adaptavist-]

You are confusing elapsed time with working time.

Your three users are each estimating it's going to take a day's work for each piece.  So the actual time taken IS three days.  It might well be delivered in one day, but it's still taking three days to do all the work.

It's not actually much use trying to track elapsed time.  If you estimated in elapsed time, you've got no way to measure the work being done, you can't get realistic predictions, and you can't cope with things like workers having time off, or team sizes changing.  Elapsed time is a poor measure because you will never manage to foresee every factor in it and it's going to fail every time.

The working time estimates can help you work out an estimate for the elapsed time.

[Ahmed Alghamdi]

never heard of elapsed time? is there such a lable on Jira that i'm not aware of?
i'm simply seeing on the right side of the screen, a time tracking tool, which includes Estimated, Remaining and Logged.?

What this time tracking is failing, is in the realization that all three developers are working on the same day, making the user story being complete in one day. If we had only one developer it would take 3 days, but because we have three developers, it will take one day!!

[Nic Brough -Adaptavist-]

No, that's my point - you are wrongly assuming that the time shown is elapsed time.  It is not.  It is tracking working time.

Your three developers are each saying "1 day", so there are three days of work to do.  It's irrelevant how many developers you have on it, it's three days of work.

[Ahmed Alghamdi]

OK, so if i'm getting you correctly, the fact that 3 developers working on the same day to produce a user story that has three tasks, a day of effort per developer per day is required meaning overall the user story would take only one day to complete, this whole thing is called tracking working time and NOT elapsed time. if this is true cool, that's my underestanding of what tracking time is. now how is this useful really? how does it help to measure if the time it gives is not accurate? in order to plan my resources, I would need to see how much resources I have and their availabilities. with this time tracking, it would gives false impression that my resources are SO overworked!! 

[Nic Brough -Adaptavist-]

Yes, it's tracking the time you estimate and take to do the work. 

>a day of effort per developer per day is required meaning overall the user story would take only one day to complete

No, it takes three days of effort to complete. The time IS accurate and it's useful because you can say "we have X days work to do".  

You can project an elapsed time from that because you know you have three developers on that day.  JIRA does not know that, and on top of that, it can't know that - what happens if one of them can't work tomorrow?  Your 1 day elapsed time estimate instantly becomes wrong, whereas the "3 days" estimate remains correct because the work is still going to take 3 days of effort.