Preheat the oven to 350 °F (180 °C) and prepare a baking dish with parchment paper.
Cook the date filling by boiling dates, water, lemon juice, and brown sugar, then simmer until dates fall apart.
Prepare the crisp mixture by combining oats, flour, brown sugar, baking powder, and butter.
Layer half of the crisp mixture in the baking dish, followed by the date mixture and the remaining crisp mixture.
Bake for 55 minutes until golden brown, then let cool before cutting into squares.
