Topic on Extension talk:MsCalendar

Fixed in version 3.0

Please be aware that this extension no longer works with the current version of Mediawiki! It looks like the current owner has no plan to update it to work with mediawiki 1.38+

Well I see updates where made but not sure if it was to fix for 1.38. I'm using 1.39.1 and this extension is not working with php 8.0.28, MySQL 5.7.38 on Centos