Regarding Schengen rules, I was told that the 90 days allowed within a 180 day period starts on the first day of entry into the Schengen zone. So if I entered a Schengen country on November 1st 2015 and stayed until December 30th (60 days). And I come back in April 1st, would I be able to stay beyond April 30th (the day the 180 day period concludes)? Or can I at least leave on April 30th and come back in a couple days and reset the 180 days period?

The 180 day period does not "reset." It is a sliding scale. For any given period of 180 days, you must not have been in Schengen more than 90 of them.

You can use this website to work it out.

http://ec.europa.eu/dgs/home-affairs...ulator_en.html

The way you imagined was how they counted 180 days until October 18, 2013. After that, a new way was implemented as described by Kerouac.

http://www.monash.edu/__data/assets/...engen-area.pdf

With the current way, if one can find ANY 180 consecutive calendar days where you were in Schengen country more than 90 calendar days, you are in violation. The number of times you exited is irrelevant. http://ec.europa.eu/dgs/home-affairs..._manual_en.pdf

You can easily sort out "I was told" rule vs. the rule in effect by a simple fact checking search. There are also Schengen calculator on the web as well as for iOS and Android.

I can never figure out that calculator. And I've read the pdf manual.

If I put my "Date of Entry/Control" as 24/06/15 (I am assuming this is the date I first entered Schengen area)
Then I put as "Previous Stays in Schengen" as 24/06/15 (date stamped on my passport) to 23/07/15 (date of departure), it gives me a message:

"The exit date 23/07/15 is later than the Entry/Control date 24/06/15
Calculation of stay is not possible"

I don't know what I'm doing wrong or I'm really not understanding how it works.

How can the date of your previous entry be the same as the date of your current entry?

Under previous you have to enter the date of your entry before the one on June 6.

Thanks, nyt. I got it now. The "date of entry" will be my re-entry date to Schengen area.