Hi htkoi,
Best I can tell, AUC is Arauca, Colombia. It's one hour ahead of US Central time (so that'd make it UTC-5). Or, AUC = EST.
It's a bit weird that they'd use this obscure abbreviation to indicate a time, as it's actually the IATA (International Air Transport Association) code for Arauca International Airport, Colombia.
Cheers,
Entropy