This plugin adds time zone functionality to Adium by letting you specify a time zone for each contact. You will then be able to see their local time in the their tooltip when you hover over them.
For more info and source code, visit my website.
Double-click the plugin icon. Adium should tell you that the plugin has been installed. Restart Adium.
Right-click (or control-click) on any contact or group in your contact list. Select "Edit Time Zone..." and choose their nearest city. Click "Set Time Zone" and then when you hover over their name, you will see their Local Time in the tooltip.
Navigate to ~/Library/Application Support/Adium 2.0/Plugins/ and drag AdiumTimeZone.AdiumPlugin out of the plugins folder, and to the Plugins (Disabled) folder or to the trash.