OFFI within 3 months, how to count the number days

[Nhung]

Hi all,
Please give me an advice, this is my situation:
I'm a PhD student in the Netherlands, according to the project I have to stay 6 months in France and 6 months in the Netherlands per year. I have the residence permit in the Netherlands for 4 years, but I cannot stay in France more than 90 days. I find out a solution is to apply for the French long-term visa, then apply for the OFFI within 3 months I enter France.
However, I don't know how they count the number of days in France since I already stay here around 2 months (1st Dec 2015). I mean now I don't have French visa and I'm going to comeback to the Netherlands and apply one but I still keep the housing contract in France. Suppose that I will get the French visa and comeback to France. Then I must apply for the OFII within 3 months entering France.I would like to know how they count the number of days I live there, I mean what is the starting day of that 3 months (the day I will comeback to France with the French long-term visa or the day I went to France without French visa on 1 Dec 2015 or the day I signed the housing contract in France?).
Thank you for your replies.
Best regards
Nhung

[steven]

Since there is no border control between France and Netherlands, there is no one to check your date of entry. It also means, that there is no evidence when exactly you entered France.

Periods of stay authorised under a residence permit or a long-stay visa shall not be taken into account in the calculation of the duration of stay on the territory of the Member States.

[Nhung]

Thank you very much Steven!

[steven]

You are welcome, let other visitors of this forum know your experience, share your case, so they can learn too.