When have often been asked about when should certain vegetables be planted. Since the answer really depends. It depends on what type of vegetables you are planting and also where you live.
The following planting / harvesting calendar from Kansas State University serves as an example to show you that different vegetables have different life span, and different planting and harvesting time.
These dates are applicable to the greater Kansas City metropolitan area. You can print out this calendar for reference if you live in the area or the climate in your area is similar to that of Kansas. Otherwise, you need to shift the dates according to the climate of your area. For example, if you are further south, you want to start earlier than these days; if your area is colder, you have more time to catch up.