If you are trying to plant in the winter in a high tunnel I came up with a harvest calculator to estimate when your winter crop will be ready based on the planting date. This estimator uses the data from Eliot Coleman’s Winter Harvest Handbook. The prediction models estimate days to maturity for a 40 day crop in an unheated cold house or cool house for Garcia’s Gardens in Indianapolis, IN. The 40 day crop is defined as one that matures in 40 days at June 1st and September 1st at four season farm in Maine. This is something like baby greens and spinach. Adjust accordingly for crops with different dtm. The models were created using the CorelPolyGUI add-on in OpenOffice.org. Sowing and harvest data was taken from Eliot Coleman’s Winter Harvest Handbook, and the daylight tables were generated from http://aa.usno.navy.mil/data/docs/Dur_OneYear.php. Coordinates were determined using maps.google.com.