My board which is made with atmega operates on battery, it should turn on every 6 hours and log some data, then go back to deep sleep to save battery consumption. I use atmega32 and not atiny because of complexity of tasks and sensors connected to the circuit.
What I have found so far, is that I can keep track of time using an RTC IC.
I've read datasheets of some RTC IC's but they don't provide any such capability as generating a signal for atmega's external interrupt at specific intervals so it can wake up from deep sleep. (What I need is something similar to cron-task, if you are familiar with it.)
And of course search terms like "atmega scheduled task" and alike did not work.
How can I efficiently (in terms of power consumption) wake atmega up from deep sleep periodically?