Hello,
The "1" at the beginning of the date isn't the label, it is supposed to be the day (like "Friday" in English). It seems that the translation in your language is wrong for the date format.
After some checks, I could see that the date format has been changed from "l, j F Y" to "L, j F Y" in nl-BE and nl-NL translation files, I reverted this modification.
If you go in the Acy configuration page, tab "Languages" then reload the nl translation, the issue should be fixed, thank you for reporting this 🙂