Let’s say I have a Verizon cell phone, my friend has a Sprint cell phone, and my other friend has a Cingular cell phone. We all have the same area code. Is there a way to know if the three phones will tell the same time without actually putting them side-by-side and comparing them? Do cell phones use a cell tower to get their time? What do cell towers use? Do the various major carriers all use the same source to set their clocks?
Thank you for the answer re: networks recording when calls are made. Do all networks (e.g., Verizon and Cingular) synchronize off the same time source? Is this something regulated by the Government?

I am planning to purchase a cell phone within the next few months. I don't know much about cell phones.. and I just came back from CES and saw some amazing cell phones. Could anyone tell me out of these three phones, which one is the best? Or describe the differences? (besides companies and how they look like)
LG Chocolate, Samsung SGH E900, Samsung SCH -u510