how can we get a timer interrupt in a specific time or date? for example I want to make a project with UNO and I'm using sleep mode and the wake up source is timer2 as far as the ATMega328p datasheet. I want to turn on an led for example everyday on 3PM and the chip is on sleep in other times of the day. so how can I set the timer? I think I have to use CTC mode of timer2 and set the OCR amount but I'm not sure how to do it. There's a project on (Link) this link in Arduino site that is perfect for this project but when I compile it, gives me an error that cant be compile for UNO.