CDT の意味は？

CDT は Central Daylight Time の略 — UTC −5、夏に米国中部ゾーン全体で観測されます。

CDT = Central Daylight Time. It's the daylight-saving form of the United States Central time zone, set at UTC −5:00 (one hour ahead of Central Standard Time, CST).

In other contexts

• "CDT" can also stand for "Cuban Daylight Time" in older references — not commonly used today.
• In medicine, CDT can mean Carbohydrate-Deficient Transferrin — unrelated to time zones.

For everything time-related on this site, CDT always refers to Central Daylight Time.