what is the date for traction type electric with calgary location?
CREATE TABLE "list_of_street_railways_in_canada" (
  "name_of_system" text,
  "location" text,
  "traction_type" text,
  "date_from" text,
  "date_to" text
);
SELECT "date_from" FROM "list_of_street_railways_in_canada" WHERE "traction_type"='electric' AND "location"='calgary';