diff --git a/types/calendar/calendar-tests.ts b/types/calendar/calendar-tests.ts
new file mode 100644
index 0000000000..0b740b0c56
--- /dev/null
+++ b/types/calendar/calendar-tests.ts
@@ -0,0 +1,16 @@
+import { Calendar } from 'calendar';
+
+const cal = new Calendar();
+cal.monthText(2019, 11);
+cal.monthText();
+
+const now = new Date();
+const year = now.getFullYear();
+const month = now.getMonth();
+
+cal.monthDates(
+    year,
+    month,
+    date => date.getMonth() === month ? date.getDate().toString() : ' ',
+    week => week.join('</td><td>'),
+);
diff --git a/types/calendar/index.d.ts b/types/calendar/index.d.ts
new file mode 100644
index 0000000000..94e3633f75
--- /dev/null
+++ b/types/calendar/index.d.ts
@@ -0,0 +1,22 @@
+// Type definitions for calendar 0.1
+// Project: https://github.com/ramalho/calendar.js#readme
+// Definitions by: Florian Keller <https://github.com/ffflorian>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+export type DayFormatter = (day: Date) => Date | string;
+export type WeekFormatter = (week: Date[]) => Date[] | string;
+
+export const version: string;
+
+export class Calendar {
+    /**
+     * @param firstWeekDay default is `0` (Sunday)
+     */
+    constructor(firstWeekDay?: number);
+
+    monthDates(year: number, month: number, dayFormatter?: DayFormatter, weekFormatter?: WeekFormatter): Date[];
+    monthDays(year: number, month: number): Date[];
+    monthText(): string;
+    monthText(year: number, month: number): string;
+    weekStartDate(date: Date): Date;
+}
diff --git a/types/calendar/tsconfig.json b/types/calendar/tsconfig.json
new file mode 100644
index 0000000000..b85b2ac529
--- /dev/null
+++ b/types/calendar/tsconfig.json
@@ -0,0 +1,23 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictFunctionTypes": true,
+        "strictNullChecks": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "calendar-tests.ts"
+    ]
+}
diff --git a/types/calendar/tslint.json b/types/calendar/tslint.json
new file mode 100644
index 0000000000..3db14f85ea
--- /dev/null
+++ b/types/calendar/tslint.json
@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }