5 files changed, 172 insertions, 0 deletions
diff --git a/date-fns/src/subISOWeekYears/benchmark.js b/date-fns/src/subISOWeekYears/benchmark.js
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+++ b/date-fns/src/subISOWeekYears/benchmark.js
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+// @flow
+/* eslint-env mocha */
+/* global suite, benchmark */
+
+import subISOWeekYears from '.'
+
+suite('subISOWeekYears', function () {
+  benchmark('date-fns', function () {
+    return subISOWeekYears(this.date, 7)
+  })
+}, {
+  setup: function () {
+    this.date = new Date()
+  }
+})
diff --git a/date-fns/src/subISOWeekYears/index.d.ts b/date-fns/src/subISOWeekYears/index.d.ts
new file mode 100644
index 0000000..78018ea
--- /dev/null
+++ b/date-fns/src/subISOWeekYears/index.d.ts
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+// This file is generated automatically by `scripts/build/typings.js`. Please, don't change it.
+
+import { subISOWeekYears } from 'date-fns'
+export default subISOWeekYears
diff --git a/date-fns/src/subISOWeekYears/index.js.flow b/date-fns/src/subISOWeekYears/index.js.flow
new file mode 100644
index 0000000..f568f0d
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+++ b/date-fns/src/subISOWeekYears/index.js.flow
@@ -0,0 +1,52 @@
+// @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: (date: Date | number, amount: number) => Date
diff --git a/date-fns/src/subISOWeekYears/index.ts b/date-fns/src/subISOWeekYears/index.ts
new file mode 100644
index 0000000..bbd396c
--- /dev/null
+++ b/date-fns/src/subISOWeekYears/index.ts
@@ -0,0 +1,39 @@
+import toInteger from '../_lib/toInteger/index'
+import addISOWeekYears from '../addISOWeekYears/index'
+import requiredArgs from '../_lib/requiredArgs/index'
+
+/**
+ * @name subISOWeekYears
+ * @category ISO Week-Numbering Year Helpers
+ * @summary Subtract the specified number of ISO week-numbering years from the given date.
+ *
+ * @description
+ * Subtract the specified number of ISO week-numbering years from the given date.
+ *
+ * ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date
+ *
+ * ### 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).
+ *
+ * - The function was renamed from `subISOYears` to `subISOWeekYears`.
+ *   "ISO week year" is short for [ISO week-numbering year](https://en.wikipedia.org/wiki/ISO_week_date).
+ *   This change makes the name consistent with
+ *   locale-dependent week-numbering year helpers, e.g., `setWeekYear`.
+ *
+ * @param {Date|Number} date - the date to be changed
+ * @param {Number} amount - the amount of ISO week-numbering years to be subtracted. Positive decimals will be rounded using `Math.floor`, decimals less than zero will be rounded using `Math.ceil`.
+ * @returns {Date} the new date with the ISO week-numbering years subtracted
+ * @throws {TypeError} 2 arguments required
+ *
+ * @example
+ * // Subtract 5 ISO week-numbering years from 1 September 2014:
+ * const result = subISOWeekYears(new Date(2014, 8, 1), 5)
+ * //=> Mon Aug 31 2009 00:00:00
+ */
+export default function subISOWeekYears(dirtyDate: Date | number, dirtyAmount: number) {
+  requiredArgs(2, arguments)
+
+  const amount = toInteger(dirtyAmount)
+  return addISOWeekYears(dirtyDate, -amount)
+}
diff --git a/date-fns/src/subISOWeekYears/test.ts b/date-fns/src/subISOWeekYears/test.ts
new file mode 100644
index 0000000..dbb4213
--- /dev/null
+++ b/date-fns/src/subISOWeekYears/test.ts
@@ -0,0 +1,62 @@
+// @flow
+/* eslint-env mocha */
+
+import assert from 'power-assert'
+import subISOWeekYears from '.'
+
+describe('subISOWeekYears', function() {
+  it('subtracts the given number of ISO week-numbering years', function() {
+    const result = subISOWeekYears(new Date(2014, 8 /* Sep */, 1), 5)
+    assert.deepEqual(result, new Date(2009, 7 /* Aug */, 31))
+  })
+
+  it('accepts a timestamp', function() {
+    const result = subISOWeekYears(new Date(2014, 8 /* Sep */, 1).getTime(), 12)
+    assert.deepEqual(result, new Date(2002, 8 /* Sep */, 2))
+  })
+
+  it('converts a fractional number to an integer', function() {
+    const result = subISOWeekYears(new Date(2014, 8 /* Sep */, 1), 5.555)
+    assert.deepEqual(result, new Date(2009, 7 /* Aug */, 31))
+  })
+
+  it('implicitly converts number arguments', function() {
+    // $ExpectedMistake
+    const result = subISOWeekYears(new Date(2014, 8 /* Sep */, 1), '5')
+    assert.deepEqual(result, new Date(2009, 7 /* Aug */, 31))
+  })
+
+  it('does not mutate the original date', function() {
+    const date = new Date(2014, 8 /* Sep */, 1)
+    subISOWeekYears(date, 12)
+    assert.deepEqual(date, new Date(2014, 8 /* Sep */, 1))
+  })
+
+  it('handles dates before 100 AD', function() {
+    const initialDate = new Date(0)
+    initialDate.setFullYear(15, 5 /* Jun */, 26)
+    initialDate.setHours(0, 0, 0, 0)
+    const expectedResult = new Date(0)
+    expectedResult.setFullYear(10, 6 /* Jul */, 2)
+    expectedResult.setHours(0, 0, 0, 0)
+    const result = subISOWeekYears(initialDate, 5)
+    assert.deepEqual(result, expectedResult)
+  })
+
+  it('returns `Invalid Date` if the given date is invalid', function() {
+    const result = subISOWeekYears(new Date(NaN), 5)
+    // @ts-expect-error
+    assert(result instanceof Date && isNaN(result))
+  })
+
+  it('returns `Invalid Date` if the given amount is NaN', function() {
+    const result = subISOWeekYears(new Date(2014, 8 /* Sep */, 1), NaN)
+    // @ts-expect-error
+    assert(result instanceof Date && isNaN(result))
+  })
+
+  it('throws TypeError exception if passed less than 2 arguments', function() {
+    assert.throws(subISOWeekYears.bind(null), TypeError)
+    assert.throws(subISOWeekYears.bind(null, 1), TypeError)
+  })
+})