Borage (herb) is classed 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
6–4 weeks before the median last spring freeze
Illinois Extension permits starting borage indoors but gives no lead time, so the offset comes from Virginia Cooperative Extension's herb publication — whose annual herb table lists borage — which sows small herb seed about six weeks before the last frost date.
Direct-sow outdoors
from the median last spring freeze to 2 weeks after
Illinois Extension sows borage directly in the garden after frost is past, a point rule that opens a two-week sowing span at the last spring freeze.
Variety assumption: Virginia Cooperative Extension lists borage as a self-sowing annual; it resents root disturbance, so direct sowing is the usual method.