Since version 1.10.0 you are able to set custom date format for the holidays. Visit Layouts tab and under Holiday date format you can insert your custom format.

Visit date cheatsheet here to see supported format:

Date Cheatsheet

Please note that default value is LL which means the day name changes based on the language you select. Some formats do not support multi language support.

If you want to add custom text between format, add them inside []. For example D[.]M[.]YYYY will output 4.1.2023