fix(components): [date-picker] support remove same months from different years (#20020)

* fix: support selecting same months from different years

* feat: add test case

* chore: adjust description

packages/components/date-picker/__tests__/date-picker.test.ts

@@ -1402,6 +1402,35 @@ describe('DatePicker months', () => {
       document.querySelectorAll('.el-month-table tr .current').length
     ).toBe(1)
   })
+
+  it('remove same months from different years', async () => {
+    const wrapper = _mount(
+      `<el-date-picker
+        type="months"
+        v-model="value"
+      />`,
+      () => ({ value: [new Date('2025-03-05'), new Date('2024-03-05')] })
+    )
+    const input = wrapper.find('input')
+    input.trigger('blur')
+    input.trigger('focus')
+    await nextTick()
+
+    const prevYearButton: HTMLElement = document.querySelector('.d-arrow-left')
+    prevYearButton.click()
+    await nextTick()
+
+    const currentMonth: HTMLElement = document.querySelector(
+      '.el-month-table tr .current'
+    )
+    currentMonth.click()
+    await nextTick()
+
+    const vm = wrapper.vm
+    expect(vm.value.length).toBe(1)
+    expect(vm.value[0].getFullYear()).toBe(2025)
+    expect(vm.value[0].getMonth()).toBe(2) // March is month 2 (0-indexed)
+  })
 })
 
 describe('DatePicker keyboard events', () => {

packages/components/date-picker/src/date-picker-com/basic-month-table.vue

@@ -232,7 +232,10 @@ const handleMonthTableClick = (event: MouseEvent | KeyboardEvent) => {
     )
     const newValue = hasClass(target, 'current')
       ? castArray(props.parsedValue).filter(
-          (d) => d?.month() !== newMonth.month()
+          (d) =>
+            // Filter out the selected month only when both year and month match
+            // This allows remove same months from different years #20019
+            d?.year() !== newMonth.year() || d?.month() !== newMonth.month()
         )
       : castArray(props.parsedValue).concat([dayjs(newMonth)])
     emit('pick', newValue)