Issue description

An error is thrown when building the example site:

ERROR invalid front matter: date: 2020年8月8日: see congo/exampleSite/content/docs/advanced-customisation/index.zh-Hans.md

Theme version

v2.9.0

Hugo version

hugo v0.135.0+extended darwin/amd64

Which browser rendering engines are you seeing the problem on?

No response

URL to sample repository or website

No response

Hugo output or build error messages

No response