Incorrect mini calendar on iCloud Calendar (Windows)

When modifying an event on icloud calendar (on windows), the mini calendar is not correct. As per my attached example, my event TEST is on friday (VEN for VENDREDI in french) the 13 of the month. The mini calendar used to chage the date shows that the 13 is on a saterday which is not correct.

[Re-Titled by Moderator]