Bring 1-1/2 cups water to simmer in medium saucepan. Add dates and simmer until very soft and thick, stirring occasionally, about 10 minutes.
Cool to room temperature and stir in vanilla.
Combine flour, sugar, oats, cinnamon, baking soda and salt in large bowl; stir to blend. Add butter using fingers until moist clumps form. Take less than half of oat mixture and press in bottom of pan to form crust. Spread date mixture over crust and sprinkle remaining oats on top and press gently.
Bake until edges are brown, about 40 minutes. Cool completely and cut into bars.