why in your documentation you have a link to https://en.wikipedia.org/wiki/Cron#CRON_expression if it is not possible to use that cron expressions? If I use a 16 14 L ? ? ....I got: 'L' is not a valid [Day] crontab field value. It must be a numeric value between 1 and 31 (all inclusive).
This just sucks, you have documentation which does not work and the cron expressions that you use are even more limited then the normal ones. If I want to run on 31 of every month or at least to use the last day of every month I can't? Damn... I don't even will talk about days 29,30. This expressions are killing me.