Steve, I'm sure you could hook into Google Calendar but getting a Pinboard presentation is not possible.

The cleanest Xara way is to create you own Pins in a separate design.
Put Pins in a grid.
If you are using Categories and Months then clone each Pin into every page of a matching Category or Month.
The Pin design would be Image, Date + (Month Link), Title, Description and Category Links.

All manual but the publish is targeted and in you main website you use an IFRAME to view the Pins' subsite.

Acorn