diff --git a/modules/home-manager/programs/calendar.nix b/modules/home-manager/programs/calendar.nix
index 0ca6823..e5c66d0 100644
--- a/modules/home-manager/programs/calendar.nix
+++ b/modules/home-manager/programs/calendar.nix
@@ -1,11 +1,14 @@
-{ config, pkgs, lib, ... }:
+{ config, lib, ... }:
 
 let
   cfg = config.local.programs.calendar;
 
   mkCalOpts = name: {
     enable = lib.mkEnableOption name;
-    package = lib.mkPackageOption pkgs name { };
+
+    # Custom package doesn't work yet.
+    # See: https://github.com/nix-community/home-manager/pull/5428
+    # package = lib.mkPackageOption pkgs name { };
   };
 in
 {
@@ -13,6 +16,20 @@ in
     khal = mkCalOpts "khal";
   };
 
-  config.home.packages =
-    lib.optional cfg.khal.enable cfg.khal.package;
+  config = {
+    accounts.calendar.basePath = "${config.xdg.dataHome}/calendars";
+
+    programs.khal = lib.mkIf cfg.khal.enable {
+      enable = true;
+      locale = rec {
+        timeformat = "%H:%M";
+        dateformat = "%Y-%m-%d";
+        longdateformat = dateformat;
+        datetimeformat = "${dateformat} ${timeformat}";
+        longdatetimeformat = datetimeformat;
+      };
+      # See: https://khal.readthedocs.io/en/latest/configure.html
+      settings = {};
+    };
+  };
 }
diff --git a/modules/nixos/configs/nix.nix b/modules/nixos/configs/nix.nix
index e0bf4a7..aa47876 100644
--- a/modules/nixos/configs/nix.nix
+++ b/modules/nixos/configs/nix.nix
@@ -42,6 +42,9 @@ in
           };
         };
       })
+      (final: prev: {
+        khal = (import inputs.nixpkgs-unstable { inherit (config.nixpkgs) system; }).khal;
+      })
       (final: prev: {
         unstable = import inputs.nixpkgs-unstable {
           inherit (config.nixpkgs) config overlays system;
diff --git a/users/jan/calendars.secret.nix b/users/jan/calendars.secret.nix
new file mode 100644
index 0000000..760366c
Binary files /dev/null and b/users/jan/calendars.secret.nix differ
diff --git a/users/jan/default.nix b/users/jan/default.nix
index 7d23168..78bcebd 100644
--- a/users/jan/default.nix
+++ b/users/jan/default.nix
@@ -56,6 +56,7 @@
   home-manager.users.jan = {
     imports = [
       ./email_accounts.secret.nix
+      ./calendars.secret.nix
       ./git
     ];
 
@@ -95,6 +96,10 @@
     local.programs.file-managers.vifm.enable = lib.mkDefault true;
 
     local.programs.aerc.enable = lib.mkDefault true;
+    local.programs.calendar.khal = {
+      enable = lib.mkDefault true;
+      # package = pkgs.unstable.khal;
+    };
 
     local.programs.communication = {
       telegram.enable = lib.mkDefault true;