Don't get angry and vote against me...

1.- You never told the RTC needed any calibration method, so what i said in the first place is that you needed a calibration method, if not it would not be as accurate as a Hardware RTC

2.- The timer works exact like a digital counter, AND it needs the cystal in order to count and it ISN'T calibrated (thing you never told) then the timer would not count as accurate as it could

3.- If your kitchen clock deviate no more than 20 seconds over the year, it is because it is calibrated and you never told it needed a calibration

4.- Only a wrong software implementation can cause missing counts???? what about increasing temperature 40°C....

5.- You pointed what it out already on many earlier postings. it was your FIRST post in THIS thread

6.- If you had a working RTC software and different from the tutorial in this site, why didn't you posted the link so we can all see the alternatives of programming RTC?

If i'm wrong then why 2 people supported me and marked your post as an incorrect answer????

It is totally immature you marked my answer as wrong just for vengeance 2 people voted againt you. I specificaly told my base was the RTC from this site and needed calibration in order to make it more accurate because your post was missing this very important thing. Deplorable behavior you can't take constructive critics