You have a formula in A27 of the
Feiertage sheet which doesn't work in my UK
locale:
Code:
=DATEVALUE(TEXT(IF(A26-31 < 1,A26,A26-31),"0#")&"."&IF(A26 > 31,"04.","03.")&B1)
It could work in any
locale by changing it to:
Code:
=DATE(B1,IF(A26>31,4,3),IF(A26-31<1,A26,A26-31))