Grace period is a specific period of time preceding the filing of a patent application, during which certain types of disclosures of the invention (for which the patent application is filed) do not destroy its novelty.
In general, in order for an invention to be patentable, the novelty criterion has to be fulfilled, that is to say, the invention should not be disclosed to the public before the patent application is filed.
However, some countries under certain circumstances do not take prior disclosures into account in determining patentability, provided they took place within a certain period of time (grace period) preceding the date of filing.
Grace period simply protects the inventor from unauthorised, or (in certain countries) authorised, disclosure of an invention before a patent is filed for. The grace period is usually 6 or 12 months.
Most of the European Patent Convention (EPC) member states adopt a ‘conditional’ patent grace period, that is to say they provide for a grace period under certain circumstances. For instance, in Germany disclosure is not to be taken into account in determining the novelty of a patent if it occurred within six months before the filing date (priority date) due to:
1. an evident abuse to the prejudice of the applicant or his predecessor in title;
2. display of the invention at an official or officially recognized exhibition.
For more information regarding the countries that grace period applies you can have access to the WIPO’s report regarding certain aspects of national/regional patent law available form here.