Birodh Som:

If you are asking about how they calculate the number of days you have remained in the country for your citizenship eligibility, the timeline does not get reset regardless of your entry and exit from the country. As long as you maintain your PR status, they deduct the number of days you have been outside of the country and only count the days you have actually spent in the country to work out your eligiblity. That's how it works in Canada. I think US system needs you to maintain your PR status for 5 years, regardless of number of days spent outside of the country, but I am not 100% sure on US one. Further, in Canada, they actually give you 1/2 credit for each day you spent in that country before you actually obtained your PR within past 4 or 5 years... I hope this answers your Q.

//YoTaBhayanaNiSom