The environment variable TZ can be used to change the timezone temporarily
I'm assuming you are in the Pacific timezone (TZ="PST8PDT") in this code snippet:
Code:
#!/bin/ksh
oldTZ="$TZ"
export TZ="EST5EDT"
orderdate=`date '+%Y%m%d'`
ordertime=`date '+%H%M%S'`
export TZ="$oldTZ"