One-liner fix for issue #773 and new unit tests to exercise that area.

Simple fix for #773.  "prove -Ilib t/CalendarToday.t t/00-roles.t" passes, as does some ad-hock queries in duckpan server.

Another first timer here.  I hit some installdeps issues on Codio, so just I installed everything thing on a local box which went smoothly.  The Codio problems I'll raise elsewhere.