GMT is not an old name for UTC. From http://www.bis.gov.uk/files/file32707.pdf http://www.bis.gov.uk/files/file32707.pdf : Coordinated Universal Time (UTC) is

GMT is not an old name for UTC. From http://www.bis.gov.uk/files/file32707.pdf http://www.bis.gov.uk/files/file32707.pdf : Coordinated Universal Time (UTC) is based on International Atomic Time (TAI), but offset by an integer number of seconds so that it remains in approximate agreement with more traditional time scales based on the Earth’s rotation (i.e. Universal Time or, equivalently, Greenwich Mean Time). There is no natural gearing between TAI and GMT and so additional ‘leap seconds’ are applied when required to keep UTC in agreement with GMT to the nearest 0.9 seconds (see notes on time scales in Annex A for background information). UTC is the global standard for civil-time keeping today. It provides the most stable time base available because it is based on TAI, but also acts as a good approximation to its antecedent, GMT, for everyday purposes.