Comment 1 for bug 1341710

to recreate, you can either:
a.) launch instance with cloud-config specifying:
    timezone: US/Eastern
b.) inside an instance run:
    sudo cloud-init single --frequency=always --name=cc_timezone US/Eastern

Either way, you'll end up with something like:

$ cat /etc/timezone
# Created by cloud-init v. 0.7.6 on Tue, 29 Jul 2014 13:49:26 +0000
US/Eastern