There are primarily three dates that are of relevance for a patent; filing date, publication date and priority date. Filing Date is the date on which application for the patent is made to respective patent office. For each patent, the publication date is the date on which particular issue of Patent Office Journal containing details of specific patent application is published. Priority date is the first date on which invention was first disclosed in any country. Where an application for patent in India (or any other country) is based on a previously filed patent application in any other country, the priority date of that patent shall be the date of the previously filed application in which the invention was first disclosed.