29.12.2017, 10:46
Yes I already figured that out 
Instead I now use Timestamp -= 172800 again, and I added the next line at the end of the TimestampToDate function;
if (month == 12) day--;
And now everything is working fine so far

Instead I now use Timestamp -= 172800 again, and I added the next line at the end of the TimestampToDate function;
if (month == 12) day--;
And now everything is working fine so far