Spitsoor, an approach I might consider is using http://www.tablesgenerator.com/html_tables.

You can create your required CSS and save the template (events.tgn) and pass that with the web address above to the owner..
Thereafter your client owner loads the template and adds rows and manipulates as required.
The template/table is saved, awaiting the next edit cycle.

The displayed code is copied to the Clipboard and saved as the same filename (events.htm) and published to a location that the owner can publish directly to.
Occasionally, you get a copy of the tgn file for save-keeping.

Your Xara design simply has an iframe to the same location.

Acorn

P.S. Your original asked for a calendar, which is a different kettle of fish.