When planting in the past, I would ask local gardeners, and plant crops when they do. This always works well, and I have yet to plant a major crop too early or too late, but I was looking for a more rigid way of planning out my planting times; I was looking for something I could sit down with a calendar, and plot out the whole season. I could ask the local gardeners for a list of planting dates, but I’d rather not bother anyone with such a list. Luckily, I stumbled onto such a calculator on a blog I was reading: Skippy’s Vegetable Garden blog.
This wonderful tool will tell you when you should plant seedlings, based on the Last Frost Date that you enter, so it should be good for most of the Middle/Northern States, and I would imagine Europe too.
So, Now I have my rigid timeline to adhere too. I hope it helps everyone as much as it has helped me.