NEW UPADTES! amazing!
I think this is the most up to date code for the lua calendar
The standard way to get calendars in conky is by cal followed by some complicated regex to make the current day show up in a different color. Other than that you don't have much control over the layout and you have to use a mono font otherwise everything is out of line.
This calendar can use any font you like and still keep aligned. You can also control many other aspects of the calendar layout.