windows 7 - where and How the computer/mobile phone time and date stored

i tried something,

i noted down the current time within my laptop(dell.. win 7) it was 12.15 PM 5 April 2014, and i did the same with my mobile phone(samsung galaxy s2, andriod jelly bean) it was 12.16 PM 5 April 2014....

. THEN i switched off my mobile phone and my laptop for for allmost approx 10 hours and switch BOTH ON again and saw the time was still synchronize and the time was perfect, how is this possible where as i was expecting the time to be delay by 10 hours of current time...

and again i tried the same with my mobile and.. this time i removed the battery also for 2 hours then it was asking me to enter time again...

can any one please tell be how this happens

For a computer, there is a battery, usually a watch style circular one. This powers a small piece of memory traditionally called CMOS. This memory stores the time and all the other BIOS settings. On a modern PC these batteries tend to last way past the computers useful life time.

A mobile phone/tablet isn't likely to have a secondary battery as they would take up too much space, but probably has a capacitor which can function as the same thing, albeit with a lot less capacity...hence the two hours before it forgot.