schengen visa rules

[salmamamdouh]

I have a schengen visa for 3 years multiple entry type C.  Would like to know if i stay in a Schengen country for 90 days, how long should i be out of Schengen territory so that i can re-enter with my multiple entry visa? And is there a maximum number of days in one year that i should not exceed? And a year in the Schengen visa is from January 1st to December 31st or starting from the date of issue?  Thank you very much in advance.

[apapunas]

This goes by so called 90/180 days rule. You can remain 90 days out of each 180 days in the Schengen zone. You need to be out of the Schengen zone for 90 days if you stay there for 90 days.