I just upgraded a few packages and was concerned that the timezone information had disappeared from /etc/conf.d/hwclock. Upon searching for the correct method to set the timezone in Gentoo, I ended up at the localization guide: http://www.gentoo.org/doc/en/guide-localization.xml This document refers to /etc/conf.d/clock (instead of hwclock) and uses uppercase variables, but judging from the number of config files I just updated these have all been changed to lowercase now. It also tells you to put the timezone in the clock/hwclock config file, but apparently this isn't required any more.
You're using OpenRC, which we don't cover in our documentation until it's marked stable. See bug #213988.
