This is the standard way to "save" your calendar as a portable file.

Export an Outlook calendar to Google Calendar - Microsoft Support

Best for importing into Google Calendar, Apple Calendar, or other apps.

Best for opening your schedule in Excel for reporting or data analysis.

Best for creating a full backup of your Outlook data, including emails and contacts. How to Download from Outlook Desktop (Classic)

Whether you need to back up your schedule, move it to another app, or analyze it in Excel, downloading your Outlook calendar is a straightforward process. Depending on whether you use the desktop app or the web version, you can export your data in several formats, including (universal calendar format), CSV (for spreadsheets), or PST (for complete backups). Quick Summary of Export Formats

The classic desktop app offers the most flexibility for downloading your calendar in different formats. 1. Export as an ICS File (iCalendar)