World Water Monitoring Day is observed on September 18 every year. This observance was established in 2003 by America's Clean Water Foundation to raise public awareness of the issues of pollution of water bodies.
Forestry and Timber Industry Worker's Day is a professional day, that is observed by people, whose profession is connected with forestry and timber industry. This international professional day is observed on the third Sunday in September in a number of CIS member countries.
Astronomy Day is annually celebrated in Armenia on September 18. This observance was established by the government of Armenia to commemorate birthday of Victor Ambartsumian, an outstanding Armenian scientist, founder of theoretical astrophysics and national hero in Armenia.