YYYY-MM-DD Format Not Working

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**Describe the bug**
When passing in a parse format of `YYYY-MM-DD` with an invalid date string of `10/12/2014`, should result in and invalid date but instead resolves to `08-14-2015`

**Expected behavior**
Should result in `date.isValid() === false`

**Information**
 - Day.js Version [e.g. v1.8.11]
 - OS: [e.g. MacOS]
 - Browser [e.g. chrome 73]

[**CodeSandbox Link**](https://codesandbox.io/s/km684x1qpo)




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### Submitted pull Requests
- [#517 fix: Add UTC mode with UTC plugin](https://issuehunt.io/r/iamkun/dayjs/pull/517)
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YYYY-MM-DD Format Not Working #555

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