<P> As the United Kingdom grew into an advanced maritime nation , British mariners kept at least one chronometer on GMT to calculate their longitude from the Greenwich meridian , which was by convention considered to have longitude zero degrees , internationally adopted in the International Meridian Conference of 1884 . Synchronisation of the chronometer on GMT did not affect shipboard time , which was still solar time . But this practice , combined with mariners from other nations drawing from Nevil Maskelyne 's method of lunar distances based on observations at Greenwich , led to GMT being used worldwide as a standard time independent of location . Most time zones were based upon GMT , as an offset of a number of hours ( and possibly a half - hour ) `` ahead of GMT '' or `` behind GMT '' . </P>
<P> As the United Kingdom grew into an advanced maritime nation , British mariners kept at least one chronometer on GMT to calculate their longitude from the Greenwich meridian , which was by convention considered to have longitude zero degrees , internationally adopted in the International Meridian Conference of 1884 . Synchronisation of the chronometer on GMT did not affect shipboard time , which was still solar time . But this practice , combined with mariners from other nations drawing from Nevil Maskelyne 's method of lunar distances based on observations at Greenwich , led to GMT being used worldwide as a standard time independent of location . Most time zones were based upon GMT , as an offset of a number of hours ( and possibly a half - hour ) `` ahead of GMT '' or `` behind GMT '' . </P>
gmt is named after a place in which country
gmt is named after a place in which country
the United Kingdom
the United Kingdom