user: Question: What day was the margin of victory 1 stroke when the tournament was Colonial National Invitation?
Columns: ['Date', 'Tournament', 'Winning score', 'Margin of victory', 'Runner(s)-up']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['May 22, 1994', 'Memorial Tournament', '−20 (67-67-67-67=268)', '5 strokes', 'Greg Norman']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Margin of victory" = '1 stroke' AND "Tournament" = 'Colonial National Invitation';