In a medium saucepan, combine the chopped dates and water. Over mediumlow heat, bring to a simmer and cook for 5 minutes. Add the sugar and lemon juice and stir until the sugar has dissolved. Bring back up to a boil and cook for 1 minute. Remove from the heat and allow to cool to room temperature.

Thoroughly butter a 9 x 13inch baking pan with 2 inch sides and line the base of it with parchment paper.

Preheat the oven to 350 degrees. In a large mixing bowl, combine the oats, flour, brown sugar, cinnamon, baking soda, and salt. Mix together well with a wooden spoon, then drizzle in the melted butter and stir to moisten evenly. Spread 1/2 of this crumb mixture in the base of the pan, then cover with an even layer of the cooled date mixture. Top the date layer with another layer of the crumb mixture and bake for 30 to 35 minutes, or until the top is golden and bubbly, and the edges have begun to caramelize. Cool on a rack, to room temperature. Run a knife around the inside edge of the pan to release, and cut into 12 squares.