"Duration" instead of end time#294

Many times, it would be much more convenient to specify the duration of the attack rather than the end time, especially for attacks that are recorded after the fact. For instance, this requires a lot more effort:

Start: Dec 24, 12:30 pm (4 keypresses and a scroll)
End: Dec 24, 2:30 pm (4 keypresses and a scroll)

But if you used duration, you could do:

Start: Dec 24, 12:30 pm (4 keypresses and a scroll)
End: +2 hours (1 scroll)

There’s probably a clever way of putting both options on a single screen (e.g., maybe have a +1/-1 hour button that automatically sets the end time)

There are already duration preset buttons there, maybe allowing users to add custom duration presets. My headaches last for ~10mins after sumatriptan injection so almost all of my recorded attacks are ~10min duration.

Thank you for your suggestion @Adam McCaughan and @Blsub6
It is always a bit tricky to find a convenient (friendly and not overwhelming) way to account for attack end time :)