Eggplant (warm-season fruiting vegetable) is classed very tender in the cited extension guidance. The timing rules below are relative to your local freeze dates — enter a location to turn them into calendar dates.
The rules this site applies
Method
Frost-relative window
Rule & reconciliation
Start seeds indoors
8–6 weeks before the median last spring freeze
Sow 8–10 weeks before the transplant window opens (UNH 8–10 weeks; Missouri G6570 6–8 weeks).
Transplant outdoors
2–4 weeks after the median last spring freeze
UNH: set out 2–3 weeks after the last frost; Purdue: very tender — at least two weeks after. Span extended to 14 days.
Seed germination soil temperature: optimum 85°F (optimum range 75–90°F); minimum 60°F, maximum 95°F. Purdue HO-186-W Table 3. Cold soil below the minimum rots seed — a reason windows and soil readings both matter.
Variety assumption: Assumes an average variety (about 65–80 days from transplant).
Hardiness classes: hardy = plant 4-6 wk before last spring frost; semi-hardy = 2-4 wk before; tender = after average last frost; very tender = at least 2 wk after. Table 2: fall planting at least 4-8 wk before first fall frost.