Endive and Escarole (cool-season leafy green) is classed semi hardy 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
Direct-sow outdoors
2 weeks before the median last spring freeze, up to the freeze date
Utah State University Extension lists endive seed in its semi-hardy Group B, planted "about 2 weeks before average last spring frost", so the point rule opens a 14-day span from last spring frost minus 14 to the frost date itself; Minnesota's earlier "as soon as the soil is workable" is superseded by the later, more frost-conservative USU interval.
Fall planting
90–76 days before the median first fall freeze
University of Minnesota Extension's direct-seeding guidance for lettuce, endive and radicchio says to "sow seed about three months before the average first fall frost date", giving a 14-day span from first fall frost minus 90 to minus 76 days.
Variety assumption: Endive and escarole are the curly-leaved and broad-leaved forms of one species (Cichorium endivia) and are treated as a single crop by Arkansas Extension; offsets assume the 85–98 day full-head types in its cultivar table.