First and last frost dates differ considerably depending on the town where you garden. GardenAction gives you the ability to set these dates to your home town in seconds. 
If you do this, all dates in GardenAction will be adjusted so that they are accurate for your home town. Sowing, planting, harvest and care dates will all be adjusted automatically.
Note that the dates are correct for six years in every seven (statistically) but local variations will occur (e.g. areas in frost pockets).