Iphone 5s

You must note that the iPhone (or any other phone) uses a Lithium Ion battery that will often show that a device has a much greater percentage of power than actually in the cell. Try charging your phone for a large amount of time to insure it is still working and then test it. To keep your battery in top condition you should charge it to 60-80% and not run it flat as this can damage to battery (unlike what your told as this is for lead acid batteries, the old type).

Please note that OPage's post is full of non-facts.

That seems normal if you can figure out how long your phone actually lasted before it turned off.

Do you remember you lock your phone before putting it in your pocket? This helps to conserve battery if your press the power button before you put it in your pocket.

9am-5pm ~ 8 hours

Did you leave any app running up front? Most people when leaving their house forget to turn on wifi which the phone will constantly searches for wifi to connect to.

You can charge your battery anytime even if it is dead. It is recommended you run your battery down once a month and charge it completely to 100% to calibrate the battery (power cycle)

I charge my phone when battery is either when it is dead or when it is about to die roughly 1-5 percent to keep the ion moving in the battery and I charge it on the computer since I noticed a better lasting battery charging from the computer than the actual outlet.