So you have ordered your seeds or are still working on it. How much time do you have to grow what you ordered?
A great reference is a cold hardiness zone map. This is a detailed map of the "zones" for the U.S. Example is Kansas City, MO. This is mostly a 5 zone, and most zones are broken into a and b. It shows that it can be a combination between 5b and 6a. My suggestion if you live in combination area, you use the lower zone for planning/growing purposes. In my part of the world due to the mountains we have 3a through 4a combination. I always plan for 3a then I know it will survive the winters here, if I am doing long term plantings.
Using this will help you plan your garden. On the back of many seed packages there is a simplified version of this with a general time frame in which to plant if you live in this area. It will also tell you if you need to start the seeds indoors or direct sow.
Using this information and your seed packets, you can start your calendar.