The U.S. went on permanent DST for the duration of World War II starting on February 9, 1942. The following quotation from /Broadcasting/ magazine of 1942-02-02 sheds some more light on abbreviations used in the U.S. during the early 1940s: : At present, times for network programs are nationally released in : accordance with their broadcasts on the East Coast and are labelled : EST. In previous years, during the months that daylight saving time : was in effect in certain parts of the country, including New York, : the designation was changed to EDST for that period. : [... T]he MBS publicity department stated that it will follow the : custom of other years and label program times as EDST. NBC said : that [...] Red Netowrk programs would be shown as EST after Feb. 9. : [...] CBS has announced that "concurrent with national daylight : saving beginning Feb. 9, Columbia network's time designation on news : releaess is Eastern Time. This phrase was chosen because the time : is no longer standard and because, with national daylight saving, : EDST seems unessential." -GAWollman