cdt is what time zone vs cst
Time zone offset: UTC - 5 hours. Note that CDT is a daylight saving time/summer time zone. It is generally only used during the summer in the places listed below, during the winter CST is used instead.
A Brief Examination of Central Daylight Time. Between the months of March and November, a modified time zone is in effect for much of the CST zone called Central Daylight Time. This modification is UTC -05:00 instead of the normal six hour offset. As mentioned earlier, the Canadian province of Saskatchewan does not participate in this practice.