The Patent Law Treaty (PLT) is a patent law multilateral treaty concluded on 1 June 2000 in Geneva, Switzerland, by 53 States and the European Patent Organisation (an intergovernmental organization). Its aim is to harmonize formal procedures such as the requirements to obtain a filing date for a patent application, the form and content of a patent application, and representation. As of November 2017, the PLT had 39 contracting states, while 59 states and the European Patent Organisation have signed the treaty. From Wikipedia
The Patent Law Treaty (PLT) was adopted in 2000 with the aim of harmonizing and streamlining formal procedures with respect to national and regional patent applications and patents and making such procedures more user friendly. With the significant exception of filing date requirements, the PLT provides the maximum sets of requirements the office of a Contracting Party may apply.