5 files changed, 400 insertions, 0 deletions
diff --git a/date-fns/src/differenceInDays/benchmark.js b/date-fns/src/differenceInDays/benchmark.js
new file mode 100644
index 0000000..2bc0f44
--- /dev/null
+++ b/date-fns/src/differenceInDays/benchmark.js
@@ -0,0 +1,23 @@
+// @flow
+/* eslint-env mocha */
+/* global suite, benchmark */
+
+import differenceInDays from '.'
+import moment from 'moment'
+
+suite('differenceInDays', function () {
+  benchmark('date-fns', function () {
+    return differenceInDays(this.dateA, this.dateB)
+  })
+
+  benchmark('Moment.js', function () {
+    return this.momentA.diff(this.momentB, 'day')
+  })
+}, {
+  setup: function () {
+    this.dateA = new Date()
+    this.momentA = moment()
+    this.dateB = new Date(this.dateA.getTime() + 604800000)
+    this.momentB = this.momentA.clone().add(7, 'days')
+  }
+})
diff --git a/date-fns/src/differenceInDays/index.d.ts b/date-fns/src/differenceInDays/index.d.ts
new file mode 100644
index 0000000..de04cde
--- /dev/null
+++ b/date-fns/src/differenceInDays/index.d.ts
@@ -0,0 +1,4 @@
+// This file is generated automatically by `scripts/build/typings.js`. Please, don't change it.
+
+import { differenceInDays } from 'date-fns'
+export default differenceInDays
diff --git a/date-fns/src/differenceInDays/index.js.flow b/date-fns/src/differenceInDays/index.js.flow
new file mode 100644
index 0000000..c799819
--- /dev/null
+++ b/date-fns/src/differenceInDays/index.js.flow
@@ -0,0 +1,55 @@
+// @flow
+// This file is generated automatically by `scripts/build/typings.js`. Please, don't change it.
+
+export type Interval = {
+  start: Date | number,
+  end: Date | number,
+}
+
+export type Locale = {
+  code?: string,
+  formatDistance?: (...args: Array<any>) => any,
+  formatRelative?: (...args: Array<any>) => any,
+  localize?: {
+    ordinalNumber: (...args: Array<any>) => any,
+    era: (...args: Array<any>) => any,
+    quarter: (...args: Array<any>) => any,
+    month: (...args: Array<any>) => any,
+    day: (...args: Array<any>) => any,
+    dayPeriod: (...args: Array<any>) => any,
+  },
+  formatLong?: {
+    date: (...args: Array<any>) => any,
+    time: (...args: Array<any>) => any,
+    dateTime: (...args: Array<any>) => any,
+  },
+  match?: {
+    ordinalNumber: (...args: Array<any>) => any,
+    era: (...args: Array<any>) => any,
+    quarter: (...args: Array<any>) => any,
+    month: (...args: Array<any>) => any,
+    day: (...args: Array<any>) => any,
+    dayPeriod: (...args: Array<any>) => any,
+  },
+  options?: {
+    weekStartsOn?: 0 | 1 | 2 | 3 | 4 | 5 | 6,
+    firstWeekContainsDate?: 1 | 2 | 3 | 4 | 5 | 6 | 7,
+  },
+}
+
+export type Duration = {
+  years?: number,
+  months?: number,
+  weeks?: number,
+  days?: number,
+  hours?: number,
+  minutes?: number,
+  seconds?: number,
+}
+
+export type Day = 0 | 1 | 2 | 3 | 4 | 5 | 6
+
+declare module.exports: (
+  dateLeft: Date | number,
+  dateRight: Date | number
+) => number
diff --git a/date-fns/src/differenceInDays/index.ts b/date-fns/src/differenceInDays/index.ts
new file mode 100644
index 0000000..5851836
--- /dev/null
+++ b/date-fns/src/differenceInDays/index.ts
@@ -0,0 +1,104 @@
+import toDate from '../toDate/index'
+import differenceInCalendarDays from '../differenceInCalendarDays/index'
+import requiredArgs from '../_lib/requiredArgs/index'
+
+// Like `compareAsc` but uses local time not UTC, which is needed
+// for accurate equality comparisons of UTC timestamps that end up
+// having the same representation in local time, e.g. one hour before
+// DST ends vs. the instant that DST ends.
+function compareLocalAsc(dateLeft: Date, dateRight: Date): number {
+  const diff =
+    dateLeft.getFullYear() - dateRight.getFullYear() ||
+    dateLeft.getMonth() - dateRight.getMonth() ||
+    dateLeft.getDate() - dateRight.getDate() ||
+    dateLeft.getHours() - dateRight.getHours() ||
+    dateLeft.getMinutes() - dateRight.getMinutes() ||
+    dateLeft.getSeconds() - dateRight.getSeconds() ||
+    dateLeft.getMilliseconds() - dateRight.getMilliseconds()
+
+  if (diff < 0) {
+    return -1
+  } else if (diff > 0) {
+    return 1
+    // Return 0 if diff is 0; return NaN if diff is NaN
+  } else {
+    return diff
+  }
+}
+
+/**
+ * @name differenceInDays
+ * @category Day Helpers
+ * @summary Get the number of full days between the given dates.
+ *
+ * @description
+ * Get the number of full day periods between two dates. Fractional days are
+ * truncated towards zero.
+ *
+ * One "full day" is the distance between a local time in one day to the same
+ * local time on the next or previous day. A full day can sometimes be less than
+ * or more than 24 hours if a daylight savings change happens between two dates.
+ *
+ * To ignore DST and only measure exact 24-hour periods, use this instead:
+ * `Math.floor(differenceInHours(dateLeft, dateRight)/24)|0`.
+ *
+ *
+ * ### v2.0.0 breaking changes:
+ *
+ * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
+ *
+ * @param {Date|Number} dateLeft - the later date
+ * @param {Date|Number} dateRight - the earlier date
+ * @returns {Number} the number of full days according to the local timezone
+ * @throws {TypeError} 2 arguments required
+ *
+ * @example
+ * // How many full days are between
+ * // 2 July 2011 23:00:00 and 2 July 2012 00:00:00?
+ * const result = differenceInDays(
+ *   new Date(2012, 6, 2, 0, 0),
+ *   new Date(2011, 6, 2, 23, 0)
+ * )
+ * //=> 365
+ * // How many full days are between
+ * // 2 July 2011 23:59:00 and 3 July 2011 00:01:00?
+ * const result = differenceInDays(
+ *   new Date(2011, 6, 3, 0, 1),
+ *   new Date(2011, 6, 2, 23, 59)
+ * )
+ * //=> 0
+ * // How many full days are between
+ * // 1 March 2020 0:00 and 1 June 2020 0:00 ?
+ * // Note: because local time is used, the
+ * // result will always be 92 days, even in
+ * // time zones where DST starts and the
+ * // period has only 92*24-1 hours.
+ * const result = differenceInDays(
+ *   new Date(2020, 5, 1),
+ *   new Date(2020, 2, 1)
+ * )
+//=> 92
+ */
+export default function differenceInDays(
+  dirtyDateLeft: Date | number,
+  dirtyDateRight: Date | number
+): number {
+  requiredArgs(2, arguments)
+
+  const dateLeft = toDate(dirtyDateLeft)
+  const dateRight = toDate(dirtyDateRight)
+
+  const sign = compareLocalAsc(dateLeft, dateRight)
+  const difference = Math.abs(differenceInCalendarDays(dateLeft, dateRight))
+
+  dateLeft.setDate(dateLeft.getDate() - sign * difference)
+
+  // Math.abs(diff in full days - diff in calendar days) === 1 if last calendar day is not full
+  // If so, result must be decreased by 1 in absolute value
+  const isLastDayNotFull = Number(
+    compareLocalAsc(dateLeft, dateRight) === -sign
+  )
+  const result = sign * (difference - isLastDayNotFull)
+  // Prevent negative zero
+  return result === 0 ? 0 : result
+}
diff --git a/date-fns/src/differenceInDays/test.ts b/date-fns/src/differenceInDays/test.ts
new file mode 100644
index 0000000..4afa6f8
--- /dev/null
+++ b/date-fns/src/differenceInDays/test.ts
@@ -0,0 +1,214 @@
+/* eslint-env mocha */
+
+import assert from 'power-assert'
+import differenceInDays from '.'
+import { getDstTransitions } from '../../test/dst/tzOffsetTransitions'
+
+describe('differenceInDays', function () {
+  it('returns the number of full days between the given dates', function () {
+    const result = differenceInDays(
+      new Date(2012, 6 /* Jul */, 2, 18, 0),
+      new Date(2011, 6 /* Jul */, 2, 6, 0)
+    )
+    assert(result === 366)
+  })
+
+  it('returns a negative number if the time value of the first date is smaller', function () {
+    const result = differenceInDays(
+      new Date(2011, 6 /* Jul */, 2, 6, 0),
+      new Date(2012, 6 /* Jul */, 2, 18, 0)
+    )
+    assert(result === -366)
+  })
+
+  it('accepts timestamps', function () {
+    const result = differenceInDays(
+      new Date(2014, 8 /* Sep */, 5, 18, 0).getTime(),
+      new Date(2014, 8 /* Sep */, 4, 6, 0).getTime()
+    )
+    assert(result === 1)
+  })
+
+  describe('edge cases', function () {
+    it('the difference is less than a day, but the given dates are in different calendar days', function () {
+      const result = differenceInDays(
+        new Date(2014, 8 /* Sep */, 5, 0, 0),
+        new Date(2014, 8 /* Sep */, 4, 23, 59)
+      )
+      assert(result === 0)
+    })
+
+    it('the same for the swapped dates', function () {
+      const result = differenceInDays(
+        new Date(2014, 8 /* Sep */, 4, 23, 59),
+        new Date(2014, 8 /* Sep */, 5, 0, 0)
+      )
+      assert(result === 0)
+    })
+
+    it('the time values of the given dates are the same', function () {
+      const result = differenceInDays(
+        new Date(2014, 8 /* Sep */, 6, 0, 0),
+        new Date(2014, 8 /* Sep */, 5, 0, 0)
+      )
+      assert(result === 1)
+    })
+
+    it('the given dates are the same', function () {
+      const result = differenceInDays(
+        new Date(2014, 8 /* Sep */, 5, 0, 0),
+        new Date(2014, 8 /* Sep */, 5, 0, 0)
+      )
+      assert(result === 0)
+    })
+
+    const dstTransitions = getDstTransitions(2017)
+    const dstOnly = dstTransitions.start && dstTransitions.end ? it : it.skip
+    const tz =
+      Intl.DateTimeFormat().resolvedOptions().timeZone || process.env.tz
+    dstOnly(
+      `works across DST start & end in local timezone: ${tz || '(unknown)'}`,
+      function () {
+        const { start, end } = dstTransitions
+        const HOUR = 1000 * 60 * 60
+        const MINUTE = 1000 * 60
+        function sameTime(t1: Date, t2: Date): boolean {
+          return (
+            t1.getHours() === t2.getHours() &&
+            t1.getMinutes() === t2.getMinutes() &&
+            t1.getSeconds() === t2.getSeconds() &&
+            t1.getMilliseconds() === t2.getMilliseconds()
+          )
+        }
+
+        assert(start !== undefined)
+        assert(end !== undefined)
+
+        if (start === undefined || end === undefined) {
+          return
+        }
+
+        // It's usually 1 hour, but for some timezones, e.g. Australia/Lord_Howe, it is 30 minutes
+        const dstOffset =
+          (end.getTimezoneOffset() - start.getTimezoneOffset()) * MINUTE
+
+        // TEST DST START (SPRING)
+
+        // anchor to one hour before the boundary
+        {
+          const a = new Date(start.getTime() - HOUR) // 1 hour before DST
+          const b = new Date(a.getTime() + 24 * HOUR - dstOffset) // 1 day later, same local time
+          const c = new Date(a.getTime() + 48 * HOUR - dstOffset) // 2 days later, same local time
+
+          assert(sameTime(a, b))
+          assert(sameTime(a, c))
+          assert(sameTime(b, c))
+          assert(differenceInDays(c, b) === 1) // normal 24-hour day
+          assert(differenceInDays(b, a) === 1) // 23 hours -> 1 day
+          assert(differenceInDays(c, a) === 2) // 47 hours -> 2 days
+        }
+        // anchor exactly, the boundary
+        {
+          const a = start // exactly when DST starts
+          const b = new Date(a.getTime() + 24 * HOUR) // 1 day later, same local time
+          const c = new Date(a.getTime() + 48 * HOUR) // 2 days later, same local time
+
+          assert(sameTime(a, b))
+          assert(sameTime(a, c))
+          assert(sameTime(b, c))
+          assert(differenceInDays(c, b) === 1) // normal 24-hour day
+          assert(differenceInDays(b, a) === 1) // normal 24-hour day
+          assert(differenceInDays(c, a) === 2) // 2 normal 24-hour days
+        }
+
+        // TEST DST END (FALL)
+
+        // make sure that diffs across a "fall back" DST boundary won't report a full day
+        // until 25 hours have elapsed.
+        {
+          const a = new Date(end.getTime() - HOUR / 2) // 1 hour before Standard Time starts
+          const b = new Date(a.getTime() + 24 * HOUR + dstOffset - 15 * MINUTE) // 1 day later, 15 mins earlier local time
+          const c = new Date(a.getTime() + 48 * HOUR + dstOffset - 15 * MINUTE) // 2 days later, 15 mins earlier local time
+
+          assert(differenceInDays(c, b) === 1) // normal 24-hour day
+          assert(differenceInDays(b, a) === 0) // 24.75 hours -> 0 full days (because hour lost to DST)
+          assert(differenceInDays(c, a) === 1) // 48.75 hours -> 1 full day (because hour lost to DST)
+        }
+        // anchor to one hour before the boundary
+        {
+          const a = new Date(end.getTime() - HOUR) // 1 hour before Standard Time start
+          const b = new Date(a.getTime() + 24 * HOUR + dstOffset) // 1 day later, same local time
+          const c = new Date(a.getTime() + 48 * HOUR + dstOffset) // 2 days later, same local time
+
+          assert(sameTime(a, b))
+          assert(sameTime(a, c))
+          assert(sameTime(b, c))
+          assert(differenceInDays(c, b) === 1) // normal 24-hour day
+          assert(differenceInDays(b, a) === 1) // 25 hours -> 1 day
+          assert(differenceInDays(c, a) === 2) // 49 hours -> 2 days
+        }
+        // anchor to one hour after the boundary
+        {
+          const a = new Date(end.getTime() + HOUR) // 1 hour after Standard Time start
+          const b = new Date(a.getTime() + 24 * HOUR) // 1 day later, same local time
+          const c = new Date(a.getTime() + 48 * HOUR) // 2 days later, same local time
+
+          assert(sameTime(a, b))
+          assert(sameTime(a, c))
+          assert(sameTime(b, c))
+          assert(differenceInDays(c, b) === 1) // normal 24-hour day
+          assert(differenceInDays(b, a) === 1) // normal 24-hour day
+          assert(differenceInDays(c, a) === 2) // 2 normal 24-hour days
+        }
+        // anchor exactly at the boundary
+        {
+          const a = end // exactly when Standard Time starts
+          const b = new Date(a.getTime() + 24 * HOUR) // 1 day later, same local time
+          const c = new Date(a.getTime() + 48 * HOUR) // 2 days later, same local time
+          assert(differenceInDays(b, a) === 1) // normal 24-hour day
+          assert(differenceInDays(c, a) === 2) // 2 normal 24-hour days
+        }
+      }
+    )
+
+    it('does not return -0 when the given dates are the same', () => {
+      function isNegativeZero(x: number): boolean {
+        return x === 0 && 1 / x < 0
+      }
+
+      const result = differenceInDays(
+        new Date(2014, 8 /* Sep */, 5, 0, 0),
+        new Date(2014, 8 /* Sep */, 5, 0, 0)
+      )
+
+      const resultIsNegative = isNegativeZero(result)
+      assert(resultIsNegative === false)
+    })
+  })
+
+  it('returns NaN if the first date is `Invalid Date`', function () {
+    const result = differenceInDays(
+      new Date(NaN),
+      new Date(2017, 0 /* Jan */, 1)
+    )
+    assert(isNaN(result))
+  })
+
+  it('returns NaN if the second date is `Invalid Date`', function () {
+    const result = differenceInDays(
+      new Date(2017, 0 /* Jan */, 1),
+      new Date(NaN)
+    )
+    assert(isNaN(result))
+  })
+
+  it('returns NaN if the both dates are `Invalid Date`', function () {
+    const result = differenceInDays(new Date(NaN), new Date(NaN))
+    assert(isNaN(result))
+  })
+
+  it('throws TypeError exception if passed less than 2 arguments', function () {
+    assert.throws(differenceInDays.bind(null), TypeError)
+    assert.throws(differenceInDays.bind(null, 1), TypeError)
+  })
+})