Many thanks to both of you.

eff-content-fonts solved the calendar issue without a restart.

Not sure what fixed the contacts one as I had to restart, but I reinstalled eff-content-fonts, fonts-ui, ttf-bpg-georgian-fonts (only named ones I have installed) and fontconfig before I rebooted.

One or some of those also fixed the web site issues too (or at least for the sites I've tried), though I only tested after the reboot.

Again, thanks.