score:5
I can't say about all countries, but for the Schengen visa the partial day that the traveler arrives is a first day in a country. And the same is true for the last day - if you are going out of country at 00:01 AM, you are using another one day.
So, if you've arrived at 1st, last day you can move out without any problem - 15th of current month.
When you are entering the country, you got stamp in your document, on this stamp are the first day of your staying.
I think, in other countries rules are the same.