D The DST column shows the months in which Daylight Saving Time, a.k.a. Summer Time, begins and ends. A blank DST box usually indicates that the location stays on Standard Time all year, although in some cases the location stays on Summer Time all year. If a location is currently on DST, add one hour to the time in the Time column. Notes DTT is common IATA code for Detroit Metropolitan Airport , Coleman A. Young International Airport and Willow Run Airport . References - includes IATA codes Aviation Safety Network - IATA and ICAO airport codes Great Circle Mapper - IATA, ICAO and FAA airport codes D