To export Google Chat history as HTML for a specific month, you can use the Google Chat: Export Chat History with all Media files Chrome extension, which allows you to select a specific date range and export to HTML format. Alternatively, you can use the Kernel Google Chat Export tool, which lets you apply date filters to select specific users and time periods before saving the backup as HTML.

If you prefer using Google's native services, you can use Google Takeout to export your data, but note that the resulting files are in JSON format, not HTML. To convert this JSON data into an HTML view, you would need to use a third-party parser or online tool that processes the Takeout archive and generates a formatted HTML page.

• Chrome Extension: Run inside Google Chat, exports DMs and Spaces to HTML with media, supports date range selection.

• Kernel Tool: Paid software (approx. $199) for Workspace admins, allows date filtering and direct export to HTML or PDF.

• Google Takeout: Free, native method, but exports only in JSON; requires external conversion to HTML.

• Manual Method: Forward specific messages to Gmail, then use the browser's Print to PDF or Save as HTML function, though this is limited to selected messages.