In calendar views, like in Calendar objects, or Date Pickers (Execute recurring/once view), or anywhere where a calender is shown, the first day of week is depending on language settings either Sunday or Monday.
If you select "German" as language for AWI, the first day in a calendar shown is Sunday.
If you select "English" as language for AWI, the first day in a calendar shown is Monday.
This behavior is wrong, also in German, the first day in a calendar should be Monday. Reason behind that is, that since 1968 (Austria) 1975 (Germany) and 1978 (Switzerland) the first day of the week is defined as Monday, only earlier than that it was Sunday (see ISO 8601: https://en.wikipedia.org/wiki/ISO_8601)
DE174491
The day of the week depends on the locale of your browser.
AWI doesn't pick the locale up correctly, which will be fixed in a future version of AWI.