Strange bug with valid.expirationDate returning incorrect result in 2020

[jwld]

General information

• Library version: 10.0.0
• Browser and OS: Chrome 127.0.6533.119 (64-bit) on MacOS 14.5

Issue description

Our test suites set the test suite time 2020-01-01 (using mockdate), and we have a test to check that valid.expirationDate will return isValid: true for "07/20". This works on versions 7 and below, but on version 8 up, it returns isValid: false.

Changing the tests to any year other than 2020 seems to work fine, but I can't work out why it doesn't work on that particular year.

To replicate it, install jest and mockdate, and then run the following test suite:

const valid = require('card-validator')
const MockDate = require('mockdate')

beforeAll(() => {
  MockDate.set('2020-01-01')
})

it('is valid', () => {
  const result = valid.expirationDate('07/20').isValid

  expect(result).toBe(true)
})

On versions 7 and below, this will pass as expected. But on versions 8 and above it fails.

Alternatively you can replicate it by simply setting your own system date to 2020-01-01, and then run console.log(valid.expirationDate('07/20')), which will incorrectly return isValid: false on versions 8 and above.