thank you for your question hope this helps.
Well without knowing the model number, here's the best I can do:1. With the ignition on, turn the radio off2a. If the radio has a "FUNC" button then press and hold that, that will bring up the initial settings menu, normally with the clock first. Use the up/down/left/right arrows to set the hours and minutes and then turn the radio back on2b. If the radio doesn't have a "FUNC" button, then hold down the "AUDIO" button and the clock should come up. Again use the up/down/left/right arrows to set the hours and minutes again.
That will work for all Pioneer radio except for the brand new ones.
For the new ones, still do step 1, but on step two hold down the knob until the menu comes up, then use the up/down/left/right arrows and set the clock as usual, then turn the radio back on.