AIX: Why does the timezone differ when using su or in crontab?

AIX: Why does the timezone differ when using su or in crontab?

3:[email protected]:/root # cat wtf.sh
echo "date"
date
echo "su - root -c date"
su - root -c date
3:[email protected]:/root #
3:[email protected]:/root # ksh wtf.sh
date
Wed Nov 9 13:15:01 MEZ 2016
su - root -c ...