September 16 - International Day for the Preservation of the Ozone Layer

September 16 was designated by the United Nations General Assembly as the International Day for the Preservation of the Ozone Layer.

This designation was made on December 19 1994, in commemoration of the date, in 1987, on which nations signed the Montreal Protocol on Substances that Deplete the Ozone Layer.
Links:
Wikipedia
United Nations

September 15 - International Day of Democracy

Throughout history, democracies have flourished, been threatened or dismantled, and re-emerged in societies all over the world. The United Nations acknowledged the resilience and universality of the principles of democracy by declaring 15 September the International Day of Democracy.
Links:
1.United Nations
2.Wikipedia
3.Global democracy day

September 8 - International Literacy Day

September 8 was proclaimed International Literacy Day by UNESCO on November 17, 1965. It was first celebrated in 1966. Its aim is to highlight the importance of literacy to individuals, communities and societies. On International Literacy Day each year, UNESCO reminds the international community of the status of literacy and adult learning globally. Celebrations take place around the world.
Links
1.United nations page
2.Literacy

August 26 - Namibia Day

Heroes' Day (also known as Namibia Day) is a national public holiday in Namibia. It is recognized by the United Nations as Namibia Day. Celebrated annually on 26 August, the day commemorates numerous events in Namibian history. Officially, the day commemorates those Namibians who died for independence, especially during the Namibian War of Independence which began on 26 August. Since Samuel Maherero's return from exile for burial in 1923, The Herero people have commemorated 26 August as a gesture of defiance.

August 12 - International Youth Day

International Youth Day (IYD) is an awareness day designated by the United Nations. The first IYD was on 12 August 2000. As with other political awareness days, such as Earth Day, the purpose of the day is to draw attention to a given set of cultural and legal issues surrounding an endangered demographic. International Youth day is on August 12 each year. It was designated by the United Nations in 1999 by the adoption of resolution 54/120
Links
1.UN Youth day

August 9 - International Day of the World's Indigenous People

The term indigenous peoples can be used to describe any ethnic group of people who inhabit a geographic region with which they have the earliest known historical connection, alongside immigrants which have populated the region and which are greater in number.
On 23 December 1994, the General Assembly decided that the International Day of the World’s Indigenous People shall be observed on 9 August every year during the International Decade of the World’s Indigenous People (resolution 49/214).
Links:
1.UN Page

July 11 - World Population Day

World Population Day is an annual event, observed on July 11, which seeks to raise awareness of global population issues. The event was established by the Governing Council of the United Nations Development Programme in 1989. It was inspired by the public interest in Five Billion Day on July 11, 1987, approximately the date on which the world's population reached five billion people.

The world population on the 20th anniversary of Five Billion Day, July 11, 2007, was estimated to have been 6,727,551,263.
LInks:
1.United Nations population fund
2.World Population Day