Originally Posted by drmozes
Unless your system has an RTC (Raspberry Pi's do not without an add-on), it'll never keep the time after a reboot/power cycle.
Just to add to that... for the cost of a RTC it would be a good thing to have one installed, because the time and trouble it saves is very welcome indeed. Once it's configured you'll never need to wonder or worry about accurate timekeeping on your Slackware ARM system again.
I like the DS3231 based RTCs because of the extreme accuracy of the controller. I bought 5 of them from eBay (like this
) for around $10 and am seriously impressed by them. Installed in seconds and configured in a few short minutes, using the I2C bus under Slackware ARM. Very accurate. Very reliable. Perfect solution for me personally.