Thanks for the details.
I tested and reproduce the issue and I confirm something is wrong with date range.
Start year and End year from Control Panel -> General -> Time and Date are not applied on blog.
Best course of action is to go at : https://dev.tiki.org/Make-a-wish
Create a report for the issue (much details as possible).
I would have suggest you to create an instance on a 18.x to give a perfect use case for our developper to understand properly and quickly the issue, but actually our instance systems are down.
Our Sys Admin team has been contacted.