March - 2013

• World Meteorological Day  - 23rd
• Earth Hour  - 23rd

April - 2013

• World Heritage Day  - 18th
• International Mother Earth Day  - 22nd
• TV-Turnoff Week - held annually in the last week of April.
• Save the Frogs Day - held annually at the end of April.

May - 2013

• OZ' Water'13  - 7th to 9th
• World Migratory Bird Day  - 11th to 12th
• National Volunteer Week  - 13th to 19th
• International Day for Biological Diversity  - 22nd
• National Reconciliation Week  - 27th to 3rd
• World No Tobacco Day - held annually on May 31st.
• Climate Ride NYC-DC - held annually in May (also in September or October).

June - 2013

• Sustainable Brands 2013 From Revolution to Renaissance San Diego, CA  3rd - 6th
  
• World Environment Day  - 5th
• National Trails Day - held annually on the first Saturday of June (U.S. and Canadian event).
• World Oceans Day  - 8th
• Global Wind Day - 15th
  
• World Day to Combat Desertification and Drought  - 17th
• Red Nose Day  - 28th
• Great American Backyard Campout - held annually in the latter part of June (U.S. event).

July - 2013

• NAIDOC Week  - 7th to 14th
• World Population Day  - 11th
• Schools Tree Day  - 26th
• National Tree Day  - 28th

August - 2013

• Jeans for Genes Day  - 2nd
• International Day for World Indigenous People  - 9th
• International Youth Day  - 12th
• World Humanitarian Day - 19th
• Keep Australia Beautiful Week  - 19th to 25th

September - 2013

• National Biodiversity Month - all month
• National Wattle Day  - 1st
• National Wildlife Day - 4th
• Walk To Work Day  - 5th
• Sustainable House Day  - 8th
• National Bilby Day  - 8th
• International Coastal Cleanup Day - held annually during the second or third Saturday of September.
• International Day for the Preservation of the Ozone Layer  - 16th
• World Parks Day  - 17th TBA
• International Day of Peace - held annually on September 21st.
• World Car-Free Day  - 22nd
• World Maritime Day  - last week of September TBA
• Climate Ride California - held annually in September or October (also in May).

October - 2013

• World Vegetarian Awareness Month - held annually during the month of October. It is kicked off by World Vegetarian Day on October 1st.
• World Habitat Day  - first Monday in October
• Junk Mail Awareness Week - held annually during the first week of October.
• World Farm Animals Day - held annually on or around October 2nd (Mahatma Gandhi's birthday).
• World Animal Day  - 4th
• International Day for Disaster Reduction  - 13th
• National Ride to Work Day  - 16th
• World Food Day - held annually on October 16th by the Food and Agriculture Organization of the United Nations.
• Take Back Your Time Day - held annually on October 24th (U.S. and Canadian event).
• Food Day - held annually in the third week of October.
• National Water Week  - third week in October
• International Day for the Eradication of Poverty  - 17th
• United Nations Day  - 24th
• National Tour of Solar Homes and Businesses - held every October throughout the United States (U.S. event).
• Climate Ride California - held annually in September or October (also in May).

November - 2013

• World Vegan Day - held annually on November 1st - kicks off World Vegan Month.
• International Day for Preventing the Exploitation of the Environment in War and Armed Conflict  - 6th
• National Recycling Week  - 11th to 17th
• World Fisheries Day  - 21st
• Buy Nothing Day - held annually in late November.

December - 2013

• International Day of People with Disability  - 3rd
• International Volunteer Day  - 5th
• Human Rights Day  - 10th
• International Mountain Day  - 11th