diff --git a/src/plugin/calendar/index.js b/src/plugin/calendar/index.js
new file mode 100644
index 00000000..87db1894
--- /dev/null
+++ b/src/plugin/calendar/index.js
@@ -0,0 +1,29 @@
+export default (o, c, d) => {
+  const LT = 'h:mm A'
+  const L = 'MM/DD/YYYY'
+  const calendarFormat = {
+    lastDay: `[Yesterday at] ${LT}`,
+    sameDay: `[Today at] ${LT}`,
+    nextDay: `[Tomorrow at] ${LT}`,
+    nextWeek: `dddd [at] ${LT}`,
+    lastWeek: `[Last] dddd [at] ${LT}`,
+    sameElse: L
+  }
+  const proto = c.prototype
+  proto.calendar = function (referenceTime, formats) {
+    const format = formats || calendarFormat
+    const referenceStartOfDay = d(referenceTime || undefined).startOf('d')
+    const diff = this.diff(referenceStartOfDay, 'd', true)
+    const sameElse = 'sameElse'
+    /* eslint-disable no-nested-ternary */
+    const retVal = diff < -6 ? sameElse :
+      diff < -1 ? 'lastWeek' :
+        diff < 0 ? 'lastDay' :
+          diff < 1 ? 'sameDay' :
+            diff < 2 ? 'nextDay' :
+              diff < 7 ? 'nextWeek' : sameElse
+    /* eslint-enable no-nested-ternary */
+    return this.format(format[retVal] || calendarFormat[retVal])
+  }
+}
+
diff --git a/test/plugin/calendar.test.js b/test/plugin/calendar.test.js
new file mode 100644
index 00000000..24dec0f7
--- /dev/null
+++ b/test/plugin/calendar.test.js
@@ -0,0 +1,81 @@
+import MockDate from 'mockdate'
+import moment from 'moment'
+import dayjs from '../../src'
+import calendar from '../../src/plugin/calendar'
+
+dayjs.extend(calendar)
+
+beforeEach(() => {
+  MockDate.set(new Date())
+})
+
+afterEach(() => {
+  MockDate.reset()
+})
+
+it('No argument && null && undefined', () => {
+  expect(dayjs().calendar()).toEqual(moment().calendar())
+  expect(dayjs().calendar(null)).toEqual(moment().calendar(null))
+  expect(dayjs().calendar(undefined)).toEqual(moment().calendar(undefined))
+})
+
+it('ReferenceTime', () => {
+  const now = '2015-01-15T14:21:22.000Z'
+  const dates = [
+    {
+      name: 'nextDay',
+      date: '2015-01-14T11:23:55.000Z',
+      result: 'Tomorrow'
+    },
+    {
+      name: 'sameDay',
+      date: '2015-01-15T11:23:55.000Z',
+      result: 'Today'
+    },
+    {
+      name: 'nextWeek',
+      date: '2015-01-09T11:23:55.000Z',
+      result: 'Thursday'
+    },
+    {
+      name: 'lastDay',
+      date: '2015-01-16T11:23:55.000Z',
+      result: 'Yesterday'
+    },
+    {
+      name: 'lastWeek',
+      date: '2015-01-21T11:23:55.000Z',
+      result: 'Last'
+    },
+    {
+      name: 'sameElse',
+      date: '2015-01-01T11:23:55.000Z',
+      result: '01/15/2015'
+    },
+    {
+      name: 'sameElse',
+      date: '2015-02-21T11:23:55.000Z',
+      result: '01/15/2015'
+    }
+  ]
+  dates.forEach((d) => {
+    const dayjsResult = dayjs(now).calendar(d.date)
+    const momentjsResult = moment(now).calendar(d.date)
+    expect(dayjsResult)
+      .toEqual(momentjsResult)
+    expect(dayjsResult.indexOf(d.result) > -1)
+      .toBe(true)
+  })
+})
+
+it('Custom format', () => {
+  const format = {
+    sameDay: '[sameDay]',
+    sameElse: '[sameElse]'
+  }
+  expect(dayjs().calendar(null, format)).toEqual(moment().calendar(null, format))
+  const now = '2015-01-15T14:21:22.000Z'
+  const nextDayWithoutFormat = '2015-01-14T11:23:55.000Z'
+  expect(dayjs(now).calendar(nextDayWithoutFormat, format))
+    .toEqual(moment(now).calendar(nextDayWithoutFormat, format))
+})
diff --git a/types/plugin/calendar.d.ts b/types/plugin/calendar.d.ts
new file mode 100644
index 00000000..a8d064fd
--- /dev/null
+++ b/types/plugin/calendar.d.ts
@@ -0,0 +1,10 @@
+import { PluginFunc, ConfigType } from 'dayjs'
+
+declare const plugin: PluginFunc
+export = plugin
+
+declare module 'dayjs' {
+  interface Dayjs {
+    calendar(referenceTime?: ConfigType, formats?: object): string
+  }
+}