Preheat oven to 350°F (175°C) and line a 9x9 inch square baking pan with parchment paper.
In a medium saucepan, combine chopped dates, water, and granulated sugar. Cook over medium heat, stirring constantly, for 5 to 8 minutes until the mixture thickens into a jam-like consistency.
Remove the date mixture from heat, stir in the lemon juice, and allow to cool to room temperature.
In a large mixing bowl, whisk together the flour, oats, brown sugar, baking soda, and salt until well combined.
Incorporate the softened butter into the dry mixture using a pastry blender or fork until a coarse, sandy crumble forms.
Firmly press exactly half of the oat crumble mixture into the bottom of the prepared baking pan to form a level base.
Spread the cooled date filling evenly over the pressed base layer using an offset spatula.
Top with the remaining oat crumble mixture, pressing down very lightly to ensure adhesion without compressing the filling.
Bake in the center of the oven for 30 to 35 minutes or until the edges are golden brown and the top is set.
Cool completely in the pan on a wire rack for at least 2 hours before slicing into 16 squares to ensure structural integrity.