If you ever wanted to know the last boot time of your Windows Mobile, here is a small free application which can show you the uptime of your mobile phone. When you boot your device it writes the current timestamp to a file \UpTime.log  and anytime after that when you run the DisplayUptime.mscr it calculates the difference between the BootTime and CurrentTime and then displays the results in the form of x Days, x Hours, x Minutes, x Seconds.

Download UpTimeLogger