Time zones
The names of time zones should be treated as proper nouns. A time zone is a geographical area. Do not specify standard time and daylight time, which refer to clock settings within a time zone at specific times of the year, unless you are referring to an event, such as a webcast, where this information is important.
Microsoft style
Central Time
Eastern Time
Coordinated Universal Time
Pacific Time
Not Microsoft style
Central Daylight Time
eastern time
eastern standard time
Pacific time
It you are referring to a time zone as a geographical area, as opposed to indicating a time within that area, make explicit reference to the time zone as such.
Microsoft style
The event begins at 21:00 Eastern Time. Broadcast times may be different in the Pacific Time ...