Web, domains and email
UTC
Abbreviation for Coordinated Universal Time
In short and in plain language
UTC is the time of reference used across the whole world.
Time zones are based on it.
Technical systems such as mail servers often give times in it. This also goes for the time spans in reports.
Definition
UTC is the worldwide reference time on which time zones are based. Technical systems such as mail servers often state times and reporting periods in UTC.