When voice announcements were first instituted, they were phrased as follows: ""National Bureau of Standards, WWV; when the tone returns, Eastern Standard Time is in 12-hour format."" After the 1967 switch to GMT, the announcement changed to ""National Bureau of Standards, WWV, Fort Collins, Colorado; next tone begins at X hours, Y minute(s), Greenwich Mean Time."" However, this format would be short-lived. The announcement was changed again to the current format in 1971. ""At the tone, X hour(s), Y minute(s), Greenwich Mean Time."" The name "Greenwich Mean Time" was changed to "Coordinated Universal Time" in 1974.