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The announcement text in GitHub Flavored Markdown. For more information about GitHub Flavored Markdown, see "[Basic writing and formatting syntax](https://docs.github.com/[email protected]/github/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax)."

Example: Very **important** announcement about _nothing_.

The time at which the announcement expires. This is a timestamp in [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601) format: `YYYY-MM-DDTHH:MM:SSZ`. To set an announcement that never expires, omit this parameter, set it to `null`, or set it to an empty string.

Example: "2021-01-01T00:00:00.000-07:00"