- 1995
- The first Open Days season, featuring 110 gardens in New York and Connecticut
- First edition of the Garden Conservancy Open Days Directory is printed
- First meeting of Open Days regional ambassadors held in Cold Spring, NY
- 1997
- First Open Days in the western U.S. are held in Carmel, CA, and Honolulu, HI
- 1998
- Janet Meakin Poor becomes first chair of Open Days and leads a national expansion of the program
- Meeting of Open Days regional ambassadors in Birmingham, AL
- 2000
- The Open Days schedule goes online with the launch of the Garden Conservancy website
- 2005
- James deGrey David becomes second national chair of Open Days
- 2006
- Hicks Garden in Austin, TX, attracts 2,452 visitors in just one day
- 2007
- Meeting of Open Days regional ambassadors in Austin, TX
- 2008
- Open Days Directory becomes complimentary to Garden Conservancy members
- 2009
- “Limestone & Water” symposium at Lady Bird Johnson Wildflower Center held with Open Day in Austin, TX
- 2013
- First Open Day held in Charleston, SC, in partnership with the Charleston Horticultural Society
- 2014
- An advisory committee of key Open Days participants from around the country meets in Cold Spring, NY, to explore the future of the program
- 2015
- The Garden Conservancy is awarded the Wilfred J. Jung Distinguished Service Medal by the Garden Writers Association (now Garden Communications International) for the Open Days program
- The Digging Deeper educational series launches to supplement Open Days self-guided garden visits
- 2016
- Printed Open Days Directory returns by popular demand after a one-year hiatus
- 2017
- James Brayton Hall becomes the President and Chief Executive Officer of the Garden Conservancy
- 2020
- Garden Conservancy board of directors forms an Open Days Committee
- The Garden Conservancy begins offering virtual talks as a way for gardeners to stay connected during the COVID pandemic
- 2021
- Open Days Directory is not printed due to the pandemic, but available online Electronic ticketing for Open Days is rolled out
- 2022
- Open Days Directory returns in print
- 2023
- Open Days attendance returns to pre-pandemic levels
- 2024
- Five gardens in Palm Springs, CA, open on March 2, our earliest Open Days date ever
- Open Days returns to Alabama, coinciding with the film documentary premiere of A Garden in Conversation: Louise Agee Wrinkle’s Southern Woodland Sanctuary in Birmingham
