Cream butter and brown sugar in a mixing bowl until smooth, about 2 minutes. Beat in eggs, one at a time, until fully incorporated. Stir in vanilla. Whisk cinnamon, salt, baking soda, and flour together in a separate bowl until evenly blended. Gradually stir flour mixture into the egg mixture until dough forms.

Divide dough into three equal portions. Place each on a square of waxed paper, wrap, and refrigerate until firm, about 1 hour.

Meanwhile, make the filling: Combine dates, pecans, water, and white sugar in a saucepan over low heat. Cook and stir until thick and paste-like, about 5 minutes. Let cool slightly.

Roll one portion of dough on a lightly floured surface into a rectangle about 1/4 inch thick. Spread one-third of the filling evenly over dough. Roll up to form a log. Repeat with remaining dough and filling. Refrigerate until firm, about 1 hour.

Preheat the oven to 350 degrees F (175 degrees C). Lightly grease 2 baking sheets.

Cut logs into 1/4-inch slices using a sharp serrated knife. Arrange slices on prepared baking sheets, spacing 1 inch apart.

Bake in preheated oven until set and lightly browned, about 15 minutes. Cool cookies on racks until firm.