Hello Dear friends.
Is PR changed in these days?
I have heard of Mozrank, what is?

SEOMoz attempt to rank pages based on their criteria. SEOMoz is software designed for SEO community. Their database would be much smaller than Google's so obviously mozrank can not be compared to pagerank

PR changes at every 3 months but this pr changes happened after long time, after more than 3 months.

MozRank refers SEOmoz’s general, logarithmically scaled 10-point measure of popularity on search engines. MozRank is very similar in purpose to the measures of static importance that are used by the search engines.MozRank shows how popular a given web page is on the web. Pages with high mozRank scores tend to rank better. The more links to a given page, the more popular it becomes.