a standard time used in the zone which includes all of Alas. except the W Aleutian Islands, corresponding to the mean solar time of the 135th meridian west of Greenwich, England: it is nine hours behind Greenwich time
See Alaska Standard Time in American Heritage Dictionary 4
noun Abbr. AST
Standard time in the ninth time zone west of Greenwich, England, reckoned at 135°W and used throughout Alaska except for the western Aleutian Islands. Also called Alaska Time.