There are 5 time zones on the NA continent and the USA encompasses 11 time zones in total, so you need to be more specific.
A Google query such as "00:00 UTC to CST" would return return 6:00 PM (18:00) the day before. CST is the central time zone in the US. The population centers of the US are in EST (Eastern) and PST (Pacific/Western).
Watch out for daylight savings time changes in summer. And just to keep things complicated, some areas in the US don't observe daylight savings time.
I hope that helps.
- Glenn W9IQ