After installing archlinux, if your time date still not correct, you can set it manually using "timedatectl" command, or automaticlly set by using "ntp".
If you using lxde, openbox, you must set the time manually too on terminal, because there still no GUI tools on that DE to set time.1. First methods using timedatectl
Okay open terminal then
Type timedatectl status
#timedatectl status
To set manually
#timedatectl set-time "YYYY-MM-DD HH:MM:SS"ex
#timedatectl set-time "2013-01-08 18:18:18"then set timedatectl status
If the local time and UTC is different try with command line below
#timedatectl set-timezone UTC
Another way using NTP
#pacman -S ntpthen Check using timedatectl status.
#ntpd -qg
When using ntpd -qg your system must be connected on internet, to get time date from server.
Now your time is set, then enjoy.
Done.