diff --git a/README.md b/README.md
index 31f01f2..7d646e9 100644
--- a/README.md
+++ b/README.md
@@ -9,15 +9,39 @@
 
 [Github repo here](https://github.com/plandek-utils/ts-time-utils)
 
-small utils for managing Time, supported by Dayjs. It is intended to be used in tests.
+small utils for managing Time, supported by `Dayjs`. It is intended to be used in tests.
 
 ## Installation
 
 `yarn add @plandek-utils/time-utils` or `npm install @plandek-utils/time-utils`.
 
+## Dependencies
+
+it requires [`timekeeper`](https://www.npmjs.com/package/timekeeper) and [`Dayjs`](https://www.npmjs.com/package/dayjs)
+
 ## Usage
 
-TBD.
+we get 2 functions:
+
+- `freezeTime(time, fn)`: freezes time to the given one, executes the given function, and resets the time before returning the result of that execution.
+- `freezeTimeAwait(time, asyncFn)`: same as `freezeTime()` but expects an async function, and it waits for its return before resetting the time
+
+```typescript
+// assume now is "2019-03-21T12:21:13.000Z"
+
+function renderTime() {
+  const d = new Date()
+  console.log(d.toISOString())
+}
+
+renderTime() // => logs "2019-03-21T12:21:13.000Z"
+
+const time = new Date("2018-01-02T13:14:15.123Z")
+const res = freezeTime(time, () => { renderTime(); return 'blah' }) // => logs "2018-01-02T13:14:15.123Z"
+console.log(res) // => logs 'blah' (freezeTime() returns the result of the passed function)
+
+renderTime() // => logs "2019-03-21T12:21:13.010Z" (time is unfrozen, let's say that a 10ms have passed)
+```
 
 ## Development, Commits, versioning and publishing
 
diff --git a/package.json b/package.json
index de640cd..ff9c6a3 100644
--- a/package.json
+++ b/package.json
@@ -49,7 +49,10 @@
   "engines": {
     "node": ">=10.0"
   },
-  "dependencies": {},
+  "dependencies": {
+    "dayjs": "^1.8.16",
+    "timekeeper": "^2.2.0"
+  },
   "devDependencies": {
     "@bitjson/npm-scripts-info": "^1.0.0",
     "@types/inquirer": "^6.5.0",
diff --git a/src/__tests__/index.spec.ts b/src/__tests__/index.spec.ts
new file mode 100644
index 0000000..56ec3de
--- /dev/null
+++ b/src/__tests__/index.spec.ts
@@ -0,0 +1,43 @@
+import dayjs from "dayjs";
+import { freezeTime, freezeTimeAwait } from "..";
+
+function nowString() {
+  const d = new Date();
+  return d.toISOString();
+}
+
+function dayjsNow() {
+  return dayjs(new Date());
+}
+
+const now = dayjsNow().subtract(1, "week");
+
+[
+  { time: now, title: "works with Dayjs" },
+  { time: now.toDate(), title: "works with Date" }
+].forEach(({ time, title }) => {
+  describe(title, () => {
+    describe("freezeTime()", () => {
+      it("executes the given expect inside of the function", () => {
+        freezeTime(time, () => {
+          expect(nowString()).toEqual(time.toISOString());
+        });
+        expect.assertions(1);
+      });
+    });
+
+    describe("freezeTimeAwait()", () => {
+      async function doShit(): Promise<string> {
+        return Promise.resolve(dayjsNow().toISOString());
+      }
+
+      it("executes the given expect inside of the function", async () => {
+        await freezeTimeAwait(time, async () => {
+          const res = await doShit();
+          expect(res).toEqual(time.toISOString());
+        });
+        expect.assertions(1);
+      });
+    });
+  });
+});
diff --git a/src/index.ts b/src/index.ts
index c18d925..81a290b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1 +1,58 @@
-export * from "./lib/my-lib";
+import { Dayjs, isDayjs } from "dayjs";
+import timekeeper from "timekeeper";
+
+/**
+ * @internal
+ */
+function getDate(time: Dayjs | Date) {
+  return isDayjs(time) ? time.toDate() : time;
+}
+
+/**
+ * Executes the given function, freezing the time first to the given `time`, and resetting the function execution (uses `timekeeper`)
+ *
+ * ```typescript
+ * // assume now is "2019-03-21T12:21:13.000Z"
+ *
+ * function renderTime() {
+ *   const d = new Date()
+ *   console.log(d.toISOString())
+ * }
+ *
+ * renderTime() // => logs "2019-03-21T12:21:13.000Z"
+ *
+ * const time = new Date("2018-01-02T13:14:15.123Z")
+ * const res = freezeTime(time, () => { renderTime(); return 'blah' }) // => logs "2018-01-02T13:14:15.123Z"
+ * console.log(res) // => logs 'blah' (freezeTime() returns the result of the passed function)
+ *
+ * renderTime() // => logs "2019-03-21T12:21:13.010Z" (time is unfrozen, let's say that a 10ms have passed)
+ * ```
+ *
+ * @param time the time that will be the new "now"
+ * @param fn function to execute, on which the time will be frozen as `time`
+ */
+export function freezeTime<T>(time: Dayjs | Date, fn: () => T): T {
+  timekeeper.freeze(getDate(time));
+  const result = fn();
+  timekeeper.reset();
+  return result;
+}
+
+/**
+ * same as `freezeTime()` but it expects an async function. It will await for the function's return and return it before resetting the time
+ *
+ * TODO: this needs concurrency testing
+ *
+ * @param time the time that will be the new "now"
+ * @param fn async function to execute, on which the time will be frozen as `time`
+ * @see freezeTime
+ */
+export async function freezeTimeAwait<T>(
+  time: Dayjs | Date,
+  fn: () => Promise<T>
+): Promise<T> {
+  timekeeper.freeze(getDate(time));
+  const result = await fn();
+  timekeeper.reset();
+  return result;
+}
diff --git a/src/lib/__tests__/my-lib.spec.ts b/src/lib/__tests__/my-lib.spec.ts
deleted file mode 100644
index 851a9d1..0000000
--- a/src/lib/__tests__/my-lib.spec.ts
+++ /dev/null
@@ -1,12 +0,0 @@
-import { identity } from "../my-lib";
-
-describe("identity()", () => {
-  it("returns the same input given", () => {
-    expect(identity(null)).toBeNull();
-    expect(identity(4)).toBe(4);
-    expect(identity("whatever ")).toBe("whatever ");
-
-    const obj = { a: 1, b: 2 };
-    expect(identity(obj)).toBe(obj);
-  });
-});
diff --git a/src/lib/my-lib.ts b/src/lib/my-lib.ts
deleted file mode 100644
index d700a34..0000000
--- a/src/lib/my-lib.ts
+++ /dev/null
@@ -1,5 +0,0 @@
-export function identity<T>(a: T): T {
-  return a;
-}
-
-export {};
diff --git a/src/types/.keep b/src/types/.keep
deleted file mode 100644
index e69de29..0000000
diff --git a/yarn.lock b/yarn.lock
index b01d1db..05eab06 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1489,6 +1489,11 @@ dateformat@^3.0.0:
   resolved "https://registry.yarnpkg.com/dateformat/-/dateformat-3.0.3.tgz#a6e37499a4d9a9cf85ef5872044d62901c9889ae"
   integrity sha512-jyCETtSl3VMZMWeRo7iY1FL19ges1t55hMo5yaam4Jrsm5EPL89UQkoQRyiI+Yf4k8r2ZpdngkV8hr1lIdjb3Q==
 
+dayjs@^1.8.16:
+  version "1.8.16"
+  resolved "https://registry.yarnpkg.com/dayjs/-/dayjs-1.8.16.tgz#2a3771de537255191b947957af2fd90012e71e64"
+  integrity sha512-XPmqzWz/EJiaRHjBqSJ2s6hE/BUoCIHKgdS2QPtTQtKcS9E4/Qn0WomoH1lXanWCzri+g7zPcuNV4aTZ8PMORQ==
+
 debug@^2.2.0, debug@^2.3.3:
   version "2.6.9"
   resolved "https://registry.yarnpkg.com/debug/-/debug-2.6.9.tgz#5d128515df134ff327e90a4c93f4e077a536341f"
@@ -5623,6 +5628,11 @@ through@2, "through@>=2.2.7 <3", through@^2.3.6:
   resolved "https://registry.yarnpkg.com/through/-/through-2.3.8.tgz#0dd4c9ffaabc357960b1b724115d7e0e86a2e1f5"
   integrity sha1-DdTJ/6q8NXlgsbckEV1+Doai4fU=
 
+timekeeper@^2.2.0:
+  version "2.2.0"
+  resolved "https://registry.yarnpkg.com/timekeeper/-/timekeeper-2.2.0.tgz#9645731fce9e3280a18614a57a9d1b72af3ca368"
+  integrity sha512-W3AmPTJWZkRwu+iSNxPIsLZ2ByADsOLbbLxe46UJyWj3mlYLlwucKiq+/dPm0l9wTzqoF3/2PH0AGFCebjq23A==
+
 tmp@^0.0.33:
   version "0.0.33"
   resolved "https://registry.yarnpkg.com/tmp/-/tmp-0.0.33.tgz#6d34335889768d21b2bcda0aa277ced3b1bfadf9"