CREATE TABLE table_1817879_2 (date_opened VARCHAR2, segment_description VARCHAR2)

What date of segment description red line mos-2 north open?
SELECT date_opened FROM table_1817879_2 WHERE segment_description = "Red Line MOS-2 North"
SELECT "date_opened" FROM "table_1817879_2" WHERE "Red Line MOS-2 North" = "segment_description"