[O] duration feature especially useful

[Jude DaShiell]

I have some devices like an iphone which is all of 4 years old and going 
on 5.  I can use org-mode to log battery recharge and battery discharge 
durations with a basic org-mode table and in the event the discharge 
duration starts dropping off sharply maybe get to a store and replace the 
phone.  I put two inactive time stamps in a field for recharge and 
discharge and beside both of those fields I have a duration field where I 
do the math and record the hours and minutes.

I have an ~/org/logs/iphone.org file and have other directories under that 
~/org/ directory too.



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