The date of Earth Overshoot Day is calculated by comparing humanity’s total yearly consumption (Ecological Footprint) with Earth’s capacity to regenerate renewable natural resources in that year (biocapacity).

Global Ecological Footprint and biocapacity metrics, in turn, are calculated each year with National Footprint Accounts. Using UN statistics, these accounts incorporate the latest data and the most updated accounting methodology (the 2017 National Footprint Accounts 2017 Edition feature 2013 data.) To estimate this year’s Earth Overshoot Day, Ecological Footprint and biocapacity are “nowcasted” to the current year using the latest data from additional sources, such as the Global Carbon Project and others.

To maintain consistency with the latest reported data and science, the Ecological Footprint metrics for all past years since 1961 (the earliest year data is available) are recalculated every year, so each year’s metrics share a common data set and the exact same accounting method. The annual dates of Earth Overshoot Day are recalculated accordingly.

Consequently, it is inaccurate to simply look at media accounts from previous years to determine past Earth Overshoot Days. Indeed, a true apples-to-apples comparison of Earth Overshoot Days can only be made using the same edition of the National Footprint Accounts. For instance, it would make no sense to compare the date of Earth Overshoot Day 2007 as it was calculated that year—and reported by the media at the time—with the date of Earth Overshoot Day 2017, because improved historical data and new findings such as lower net carbon sequestration by forests have slightly shifted the results. Even a few percentage points change can shift the date of Earth Overshoot Day by a good number of days.

This is why, ultimately, the precise Earth Overshoot Day date for each year is less significant than the sheer magnitude of the ecological overshoot, as well as the overall trend of the date progression year over year—which, as you now understand, is rigorously identical to that of the Ecological Footprint (given the fact that biocapacity remains basically unchanged.) Over the last decades, the date has been creeping up the calendar every year, although at a slowing rate.

The dates of past Earth Overshoot Days, as calculated with the National Footprint Accounts 2017 Edition, are:

Wednesday, August 02, 2017

Wednesday, August 03, 2016

Tuesday, August 04, 2015

Monday, August 04, 2014

Monday, August 05, 2013

Monday, August 06, 2012

Friday, August 05, 2011

Monday, August 09, 2010

Thursday, August 20, 2009

Saturday, August 16, 2008

Wednesday, August 15, 2007

Monday, August 21, 2006

Friday, August 26, 2005

Thursday, September 02, 2004

Wednesday, September 10, 2003

Thursday, September 19, 2002

Sunday, September 23, 2001

Saturday, September 23, 2000

Thursday, September 30, 1999

Thursday, October 01, 1998

Tuesday, September 30, 1997

Wednesday, October 02, 1996

Thursday, October 05, 1995

Tuesday, October 11, 1994

Wednesday, October 13, 1993

Tuesday, October 13, 1992

Friday, October 11, 1991

Saturday, October 13, 1990

Friday, October 13, 1989

Sunday, October 16, 1988

Saturday, October 24, 1987

Friday, October 31, 1986

Tuesday, November 05, 1985

Thursday, November 08, 1984

Tuesday, November 15, 1983

Tuesday, November 16, 1982

Thursday, November 12, 1981

Tuesday, November 04, 1980

Tuesday, October 30, 1979

Wednesday, November 08, 1978

Saturday, November 12, 1977

Wednesday, November 17, 1976

Monday, December 01, 1975

Thursday, November 28, 1974

Tuesday, November 27, 1973

Sunday, December 10, 1972

Tuesday, December 21, 1971