How to Automatically differentiate the date without "Year" at last.

You could unpivot the columns to get the dates in one column.

Then add an index.

If the cutoff is 31.12, you could note the index value of this (might be 365 if you have a whole year of current data) and add a year column with an 'if' statement dependent on the index being higher or lower than the 31.12 index (e.g.365).*

Then merge the day/month column with the year column to get a valid date column.

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* -> with more work this could be dynamic i.e. not comparing to a hardcoded value but at least you could prove the algorithm by hardcoding it.