thx for this idea but it does not work for me

I made something that gives the same output your code should give but this is not what i am searching for :
Code:
for mytimestamp in $(cat logs| awk -F";" '{ print $1; }'); do echo $(date -d “1970-01-01 UTC+0100 $mytimestamp seconds”); done
What i want is to replace all the timestamps (first field) in a log file with the date in UTC+0100 format but i want to keep the other fields (file scheme)...