From b33d2abd8f44fa0128b722030168c0f33dc5860b Mon Sep 17 00:00:00 2001
From: Nickolas Kenyeres <nickolas@helpscout.com>
Date: Mon, 11 Jan 2021 17:30:27 -0500
Subject: [PATCH] Fix issue with incorrectly computed isMonthInThePast result

---
 src/components/Datepicker/Datepicker.utils.js | 11 +++++----
 .../Datepicker/Datepicker.utils.test.js       | 23 ++++++++++---------
 2 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/src/components/Datepicker/Datepicker.utils.js b/src/components/Datepicker/Datepicker.utils.js
index ade460702..b95e0a5a5 100644
--- a/src/components/Datepicker/Datepicker.utils.js
+++ b/src/components/Datepicker/Datepicker.utils.js
@@ -47,11 +47,14 @@ export function isToday(someDate) {
  */
 export function isMonthInThePast(someDate) {
   const today = new Date()
+  const thisYear = today.getFullYear()
+  const someYear = someDate.getFullYear()
 
-  return (
-    someDate.getFullYear() <= today.getFullYear() &&
-    someDate.getMonth() < today.getMonth()
-  )
+  if (someYear === thisYear) {
+    return someDate.getMonth() < today.getMonth()
+  }
+
+  return someYear < thisYear
 }
 
 export function isInsideRange({ check, to, from }) {
diff --git a/src/components/Datepicker/Datepicker.utils.test.js b/src/components/Datepicker/Datepicker.utils.test.js
index 034460533..6589cee96 100644
--- a/src/components/Datepicker/Datepicker.utils.test.js
+++ b/src/components/Datepicker/Datepicker.utils.test.js
@@ -34,17 +34,18 @@ describe('Datepicker Utils', () => {
     expect(isToday(new Date(1992, 3, 24))).toBeFalsy()
   })
 
-  test('isMonthInThePast', () => {
-    const currentDate = new Date()
-    const pastDate = new Date(2020, 5, 29)
-    const futureDate = new Date(
-      currentDate.getFullYear,
-      currentDate.getMonth + 1,
-      4
-    )
-
-    expect(isMonthInThePast(pastDate)).toBeTruthy()
-    expect(isMonthInThePast(futureDate)).toBeFalsy()
+  test.each([
+    [new Date(2020, 10, 29), new Date(2020, 5, 29), true],
+    [new Date(2021, 1, 11), new Date(2020, 5, 29), true],
+    [new Date(2021, 1, 11), new Date(2021, 1, 11), false],
+    [new Date(2021, 1, 11), new Date(2021, 1, 12), false],
+  ])('isMonthInThePast(%i)', (mockDate, someDate, expected) => {
+    const spyDateFn = jest
+      .spyOn(global, 'Date')
+      .mockImplementation(() => mockDate)
+    expect(isMonthInThePast(someDate)).toEqual(expected)
+    expect(spyDateFn).toHaveBeenCalled()
+    spyDateFn.mockRestore()
   })
 
   test('getValidDateTimeString', () => {