- The Earth Day 2012 content was available from April 22nd to May 4th, 2012.
- The Earth Day 2013 content was available from April 16th to April 24th, 2013.
- The Earth Day 2014 content was available from April 22nd to May 25th, 2014.
- The 2014 event originally didn't have a banner advert in game until May 11th, 2014 in build 25838.0
- In 2009, the United Nations designated April 22nd as International Mother Earth Day, and Earth Day is planned for April 22nd in all years up until at least 2015.
Link to Carbon's Earth Day 2012 blog post