How to convert the dates from the YY:DD forma to MM/dd/YYYY format

Hello,

I have a column with dates in the format YY:DD [here DD stands for day of
the year]. Is there a way to have a column that represents the same dates in
the normal MM/dd/YYYY format?
[MM=month#, dd=day# (day of the month), YYYY=year]

Thank you!