diff --git a/ocaml-pkgs/dates_calc.nix b/ocaml-pkgs/dates_calc.nix
new file mode 100644
index 0000000..f106c9a
--- /dev/null
+++ b/ocaml-pkgs/dates_calc.nix
@@ -0,0 +1,41 @@
+{
+  lib,
+  fetchFromGitHub,
+  buildDunePackage,
+  alcotest,
+  qcheck,
+  python3,
+}:
+
+buildDunePackage rec {
+  pname = "dates_calc";
+  version = "0.0.7";
+
+  minimalOCamlVersion = "4.11";
+  duneVersion = "3";
+
+  src = fetchFromGitHub {
+    owner = "catalalang";
+    repo = "dates-calc";
+    rev = version;
+    sha256 = "sha256-MQpQZLXu+8Q9JLZ329KqO5O/qSO+4Tm7TDh0/OPJs0c=";
+  };
+
+  propagatedBuildInputs = [ ];
+  nativeBuildInputs = [
+    python3
+  ];
+
+  doCheck = true;
+  checkInputs = [
+    alcotest
+    qcheck
+  ];
+
+  meta = {
+    description = "Date calculation library";
+    license = lib.licenses.asl20;
+    maintainers = [ lib.maintainers.niols ];
+    homepage = "https://github.com/catalalang/dates-calc";
+  };
+}