One if you registered at the police station they give you a slip telling you when your last day is in China. If you didn't calculate 90days from the 9th of March and it is counted as soon as the customs officer stamps that red circle in your passport

hi, thanks, I didn't get that slip of paper because I got registered through some friends, but what I am confused about how to calculate this 90 days. If it said 90 days AFTER entry I understand that as I start to count from 10 of March and in this case the 7 of June is the

 90-thy day. When I entered Hong Kong on the stamp in my passport  was stated that  I am permitted to stay 90 days FROM the date showed, so in this case I understand the date on the stamp is the first day to count. But maybe I get it wrong

The way it is counted is like this.  You entered March 9, 2012.  On March 10, you will be here one day, on March 11 it will be two days, and so forth.

Your 90th day will be on June 7th, 2012.  But be aware, Your 90 days will expire at the time you entered on March 9, not at midnight of June 7 to 8.   Make sure you depart China BEFORE the time you entered on March 9 to be OK, even if that will mean a few hours wait at airport in Hong Kong.

Thank you guys, so it's look like I'll have to take the plane the earlier day as this one leaves China 5 to midnight on June 7th  ;-(

I'm just surprised they could be really so strict  about one day or even couple of hours.