MacOS – Font of calendar in Preference pane of macOS

You can also use font identifiers for this, in case they have this in their database.

https://developer.apple.com/design/human-interface-guidelines/macos/visual-design/typography/

This suggests SF pro for macOS in recent versions.

Since its introduction, San Francisco has gradually replaced most of Apple's other typefaces on their software and hardware products and for overall branding[13] and has replaced Helvetica Neue and Lucida Grande as the system typeface of macOS and iOS since OS X El Capitan and iOS 9.[14][3][15] Apple uses it on its website and for its product wordmarks, where it replaced Myriad Pro. It is also used on the keyboard of the 2015 MacBook and on the 2016 MacBook Pro, replacing VAG Rounded.[16] It is also used as Apple's corporate typeface.[17]

Apple restricts the usage of the typeface by others. It is licensed to registered third-party developers only for the design and development of applications for Apple's platforms.[3]

https://en.wikipedia.org/wiki/San_Francisco_(sans-serif_typeface)#Usage