diff --git a/index.test-d.ts b/index.test-d.ts
index 8d85770..8637ed9 100644
--- a/index.test-d.ts
+++ b/index.test-d.ts
@@ -15,7 +15,7 @@ expectAssignable<Promise<number>>(cache.set('key', 1));
 expectAssignable<Promise<boolean>>(cache.set('key', true));
 expectAssignable<Promise<[boolean, string]>>(cache.set('key', [true, 'string']));
 expectAssignable<Promise<Record<string, any[]>>>(cache.set('key', {wow: [true, 'string']}));
-expectAssignable<Promise<number>>(cache.set('key', 1, 1));
+expectAssignable<Promise<number>>(cache.set('key', 1, {days: 1}));
 
 const cachedPower = cache.function(async (n: number) => n ** 1000);
 expectType<(n: number) => Promise<number>>(cachedPower);
@@ -42,14 +42,14 @@ expectNotAssignable<Promise<number>>(cache.function(identity)('1'));
 
 expectType<(n: string) => Promise<number>>(
 	cache.function(async (n: string) => Number(n), {
-		maxAge: 20
+		maxAge: {days: 20}
 	})
 );
 
 expectType<(n: string) => Promise<number>>(
 	cache.function(async (n: string) => Number(n), {
-		maxAge: 20,
-		staleWhileRevalidate: 5
+		maxAge: {days: 20},
+		staleWhileRevalidate: {days: 5}
 	})
 );
 
diff --git a/index.ts b/index.ts
index b5eba9f..5aafe62 100644
--- a/index.ts
+++ b/index.ts
@@ -1,4 +1,5 @@
 import {isBackgroundPage} from 'webext-detect-page';
+import toMilliseconds, {TimeDescriptor} from '@sindresorhus/to-milliseconds';
 
 // @ts-ignore
 // eslint-disable-next-line @typescript-eslint/promise-function-async
@@ -13,8 +14,8 @@ const getPromise = (executor: () => void) => <T>(key?): Promise<T> => new Promis
 	});
 });
 
-function daysInTheFuture(days: number): number {
-	return Date.now() + (1000 * 3600 * 24 * days);
+function timeInTheFuture(time: TimeDescriptor): number {
+	return Date.now() + toMilliseconds(time);
 }
 
 // @ts-ignore
@@ -59,7 +60,7 @@ async function get<TValue extends Value>(key: string): Promise<TValue | undefine
 	return cachedItem.data;
 }
 
-async function set<TValue extends Value>(key: string, value: TValue, maxAge = 30 /* days */): Promise<TValue> {
+async function set<TValue extends Value>(key: string, value: TValue, maxAge: TimeDescriptor = {days: 30}): Promise<TValue> {
 	if (typeof value === 'undefined') {
 		// @ts-ignore This never happens in TS because `value` can't be undefined
 		return;
@@ -69,7 +70,7 @@ async function set<TValue extends Value>(key: string, value: TValue, maxAge = 30
 	await _set({
 		[internalKey]: {
 			data: value,
-			maxAge: daysInTheFuture(maxAge)
+			maxAge: timeInTheFuture(maxAge)
 		}
 	});
 
@@ -104,8 +105,8 @@ async function clear(): Promise<void> {
 }
 
 interface MemoizedFunctionOptions<TArgs extends any[], TValue> {
-	maxAge?: number;
-	staleWhileRevalidate?: number;
+	maxAge?: TimeDescriptor;
+	staleWhileRevalidate?: TimeDescriptor;
 	cacheKey?: (args: TArgs) => string;
 	shouldRevalidate?: (cachedValue: TValue) => boolean;
 }
@@ -116,7 +117,7 @@ function function_<
 	TArgs extends Parameters<TFunction>
 >(
 	getter: TFunction,
-	{cacheKey, maxAge = 30, staleWhileRevalidate = 0, shouldRevalidate}: MemoizedFunctionOptions<TArgs, TValue> = {}
+	{cacheKey, maxAge = {days: 30}, staleWhileRevalidate = {days: 0}, shouldRevalidate}: MemoizedFunctionOptions<TArgs, TValue> = {}
 ): TFunction {
 	const getSet = async (key: string, args: TArgs): Promise<TValue | undefined> => {
 		const freshValue = await getter(...args);
@@ -125,7 +126,9 @@ function function_<
 			return;
 		}
 
-		return set<TValue>(key, freshValue, maxAge + staleWhileRevalidate);
+		const milliseconds = toMilliseconds(maxAge) + toMilliseconds(staleWhileRevalidate);
+
+		return set<TValue>(key, freshValue, {milliseconds});
 	};
 
 	return (async (...args: TArgs) => {
@@ -138,7 +141,7 @@ function function_<
 		}
 
 		// When the expiration is earlier than the number of days specified by `staleWhileRevalidate`, it means `maxAge` has already passed and therefore the cache is stale.
-		if (daysInTheFuture(staleWhileRevalidate) > cachedItem.maxAge) {
+		if (timeInTheFuture(staleWhileRevalidate) > cachedItem.maxAge) {
 			setTimeout(getSet, 0, userKey, args);
 		}
 
diff --git a/package.json b/package.json
index 2a29e26..7271fc2 100644
--- a/package.json
+++ b/package.json
@@ -69,6 +69,7 @@
     ]
   },
   "dependencies": {
+    "@sindresorhus/to-milliseconds": "^1.2.0",
     "webext-detect-page": "^2.0.2"
   },
   "devDependencies": {
diff --git a/readme.md b/readme.md
index f8700e5..19f3973 100644
--- a/readme.md
+++ b/readme.md
@@ -36,7 +36,9 @@ import cache from 'webext-storage-cache';
 (async () => {
 	if (!await cache.has('unique')) {
 		const cachableItem = await someFunction();
-		await cache.set('unique', cachableItem, 3 /* days */);
+		await cache.set('unique', cachableItem, {
+			days: 3
+		});
 	}
 
 	console.log(await cache.get('unique'));
@@ -49,7 +51,9 @@ The same code could be also written more effectively with `cache.function`:
 import cache from 'webext-storage-cache';
 
 const cachedFunction = cache.function(someFunction, {
-	maxAge: 3,
+	maxAge: {
+		days: 3
+	},
 	cacheKey: () => 'unique'
 });
 
@@ -88,9 +92,9 @@ const url = await cache.get('cached-url');
 
 Type: `string`
 
-### cache.set(key, value, maxAge /* in days */)
+### cache.set(key, value, maxAge)
 
-Caches the given key and value for a given amount of days. It returns the value itself.
+Caches the given key and value for a given amount of time. It returns the value itself.
 
 ```js
 const info = await getInfoObject();
@@ -109,10 +113,10 @@ Type: `string | number | boolean` or `array | object` of those three types.
 
 #### maxAge
 
-Type: `number`<br>
-Default: 30
+Type: [`TimeDescriptor`](https://github.com/sindresorhus/to-milliseconds#input)<br>
+Default: `{days: 30}`
 
-The number of days after which the cache item will expire.
+The amount of time after which the cache item will expire.
 
 ### cache.delete(key)
 
@@ -175,22 +179,26 @@ cachedOperate(1, 2, 3);
 
 ##### maxAge
 
-Type: `number`<br>
-Default: 30
+Type: [`TimeDescriptor`](https://github.com/sindresorhus/to-milliseconds#input)<br>
+Default: `{days: 30}`
 
-The number of days after which the cache item will expire.
+The amount of time after which the cache item will expire.
 
 ##### staleWhileRevalidate
 
-Type: `number`<br>
-Default: `0` (disabled)
+Type: [`TimeDescriptor`](https://github.com/sindresorhus/to-milliseconds#input)<br>
+Default: `{days: 0}` (disabled)
 
-Specifies how many additional days an item should be kept in cache after its expiration. During this extra time, the item will still be served from cache instantly, but `getter` will be also called asynchronously to update the cache. A later call should return an updated and fresher item.
+Specifies how much longer an item should be kept in cache after its expiration. During this extra time, the item will still be served from cache instantly, but `getter` will be also called asynchronously to update the cache. A later call will return the updated and fresher item.
 
 ```js
 const cachedOperate = cache.function(operate, {
-	maxAge: 10,
-	staleWhileRevalidate: 2
+	maxAge: {
+		days: 10
+	},
+	staleWhileRevalidate: {
+		days: 2
+	}
 });
 
 cachedOperate(); // It will run `operate` and cache it for 10 days
diff --git a/test/index.js b/test/index.js
index 50ec89c..fe518cd 100644
--- a/test/index.js
+++ b/test/index.js
@@ -2,11 +2,12 @@ import test from 'ava';
 import sinon from 'sinon';
 import './_fixtures.js';
 import cache from '../index.js';
+import toMilliseconds from '@sindresorhus/to-milliseconds';
 
 const getUsernameDemo = async name => name.slice(1).toUpperCase();
 
-function daysInTheFuture(days) {
-	return Date.now() + (1000 * 3600 * 24 * days);
+function timeInTheFuture(time) {
+	return Date.now() + toMilliseconds(time);
 }
 
 function createCache(daysFromToday, wholeCache) {
@@ -15,7 +16,7 @@ function createCache(daysFromToday, wholeCache) {
 			.withArgs(key)
 			.yields({[key]: {
 				data,
-				maxAge: daysInTheFuture(daysFromToday)
+				maxAge: timeInTheFuture({days: daysFromToday})
 			}});
 	}
 }
@@ -55,12 +56,12 @@ test.todo('set() with past maxAge should throw');
 
 test.serial('set() with value', async t => {
 	const maxAge = 20;
-	await cache.set('name', 'Anne', maxAge);
+	await cache.set('name', 'Anne', {days: maxAge});
 	const arguments_ = chrome.storage.local.set.lastCall.args[0];
 	t.deepEqual(Object.keys(arguments_), ['cache:name']);
 	t.is(arguments_['cache:name'].data, 'Anne');
-	t.true(arguments_['cache:name'].maxAge > daysInTheFuture(maxAge - 0.5));
-	t.true(arguments_['cache:name'].maxAge < daysInTheFuture(maxAge + 0.5));
+	t.true(arguments_['cache:name'].maxAge > timeInTheFuture({days: maxAge - 0.5}));
+	t.true(arguments_['cache:name'].maxAge < timeInTheFuture({days: maxAge + 0.5}));
 });
 
 test.serial('function() with empty cache', async t => {
@@ -96,8 +97,8 @@ test.serial('function() with empty cache and staleWhileRevalidate', async t => {
 
 	const spy = sinon.spy(getUsernameDemo);
 	const call = cache.function(spy, {
-		maxAge,
-		staleWhileRevalidate
+		maxAge: {days: maxAge},
+		staleWhileRevalidate: {days: staleWhileRevalidate}
 	});
 
 	t.is(await call('@anne'), 'ANNE');
@@ -109,8 +110,8 @@ test.serial('function() with empty cache and staleWhileRevalidate', async t => {
 	t.is(arguments_['cache:@anne'].data, 'ANNE');
 
 	const expectedExpiration = maxAge + staleWhileRevalidate;
-	t.true(arguments_['cache:@anne'].maxAge > daysInTheFuture(expectedExpiration - 0.5));
-	t.true(arguments_['cache:@anne'].maxAge < daysInTheFuture(expectedExpiration + 0.5));
+	t.true(arguments_['cache:@anne'].maxAge > timeInTheFuture({days: expectedExpiration - 0.5}));
+	t.true(arguments_['cache:@anne'].maxAge < timeInTheFuture({days: expectedExpiration + 0.5}));
 });
 
 test.serial('function() with fresh cache and staleWhileRevalidate', async t => {
@@ -120,8 +121,8 @@ test.serial('function() with fresh cache and staleWhileRevalidate', async t => {
 
 	const spy = sinon.spy(getUsernameDemo);
 	const call = cache.function(spy, {
-		maxAge: 1,
-		staleWhileRevalidate: 29
+		maxAge: {days: 1},
+		staleWhileRevalidate: {days: 29}
 	});
 
 	t.is(await call('@anne'), 'ANNE');
@@ -143,8 +144,8 @@ test.serial('function() with stale cache and staleWhileRevalidate', async t => {
 
 	const spy = sinon.spy(getUsernameDemo);
 	const call = cache.function(spy, {
-		maxAge: 1,
-		staleWhileRevalidate: 29
+		maxAge: {days: 1},
+		staleWhileRevalidate: {days: 29}
 	});
 
 	t.is(await call('@anne'), 'ANNE');