Now, the detail-oriented people among you will notice that I didn't say anyone was right or wrong, and I didn't use strong words such as should hyphenate or must hyphenate. I chose my words carefully because the rules about hyphens can hardly be called rules; there are so many exceptions it's making me crazy.
See full time zone map. Some places observe daylight saving time/summer time during the summer, and therefore use AKDT (Alaska Daylight Time) in the summer. An email sent from someone in the Alaska Standard Time (AKST) time zone will have the time zone listed as -0900 in the headers of the email. (However, -0900 does not have to be in Alaska Standard Time, as other time zones could have the same UTC offset).
Time zones with the GMT -8:00 h offset: 1  AKDT - Alaska Daylight Time. 2  PST - Pacific Standard Time. 3  YDT - Yukon Daylight Time. 4  PST - Pitcairn Standard Time. 5  U - Uniform Time Zone.