Differences in hardiness zones and seasonal weather between these sources and where you garden may require you to adjust timing accordingly.
When to Plant Vegetables Tool (webpage)
This allows you to enter your location and get a spring and fall planting schedule. This link defaults to Ohio, but you can enter specific location. From The National Gardening Association.
April – Time to Start Sweet Potato Slips
Growing sweet potatoes in central Ohio can be successful and productive. If you want to grow from your own sweet potato slips, now is the time to get started. Sweet potato slips are the sprouts that grow from a sweet potato “root.” (Unlike regular potatoes, sweet potatoes are not tubers.) If you grew sweet potatoes last year and still have some in storage, these work well. Otherwise you can select locally grown organic sweet potatoes from the market. These will be selected for our climate (locally grown) and will most likely NOT have been treated to resist sprouting (organic). (read more)