When dig up potatoes: “Late in season”. What is “Late?

Question

What exactly is “late in Season” for potatoes that were planted late April

Answer 1

If you planted potatoes in April, they will be mature and ready to harvest anywhere from two and a half to four months later. So, late in the season would be referencing the summer season.
However, if you want "new" potatoes, or smaller tender potatoes, you can harvest them within even a few weeks after planting. For fully mature potatoes, wait until a couple week after the green foliage has died. Here's a link for several articles about growing potatoes:
https://www.gardeningknowhow.com/search?q=new%20potatoes