To convert 18 UTC into your local time, subtract 6 hours, to get 12 CST. During daylight saving (summer) time, you would only subtract 5 hours, so 18 UTC would convert to 13 CDT. Or, let's say you're in Paris, France, which is in Central European Time. To convert 18 UTC into your local time, add 1 hour, to get 19 CET.
