Nautical time to the zero zone, and A–M (except J) to the east and N–Y to the west (J may be assigned to local time in non-nautical applications — zones M and Y have the same clock time but differ by 24 hours: a full day). These can be vocalized using the NATO phonetic alphabet which pronounces the letter "Z" as "Zulu", leading to the use of the term "Zulu Time" for Greenwich Mean Time, or UT1 from January 1, 1972 onward. Zone Z runs from 7°30′W to 7°30′E longitude, while zone A runs from 7°30′E to 22°30′E longitude, etc. These nautical
Nautical time maritime usage, GMT retains its historical meaning of UT1, the mean "solar" time at Greenwich. UTC, "atomic" time at Greenwich, is too inaccurate, differing by as much as 0.9 seconds from UT1, creating an error of of a minute of longitude at all latitudes and which is at the equator but less at higher latitudes, varying roughly by the cosine of the latitude. However, DUT can be added to UTC to correct it to within 50 milliseconds of UT1, reducing the error to only . In practice, nautical times are used only for radio communication, etc. Aboard the ship, e.g.