The Minicalendar cannot be previewed due to the following syntaxt error
In general, if the message is not clear, we suggest that you try to generate the diary. The error messages, for minicalendar tokens, during diary generation are more informative than during script previewing.
One special case that happens often, is using, for example, [mc01] instead of [mc001] as a minicalendar marker. The syntax error message is then of the form :
'01:' is not an integer value
Q++ does not try to understand [mc01] as [mc001], which it easily could do, because the source of this error could be due to the user meaning to have [mc001], but it could also be a typographical error when trying to type [mc010] or [mc011] or [mc012]. If Q++ automatically decided which of these corrections to use, it could make a hard to discover wrong choice.