Celestial Navigation · Time — Zone Description
To convert zone time to GMT in west longitude, the zone description is:
- ASubtracted from zone time
- BIgnored
- CAdded to zone time✓ Correct
- DMultiplied by longitude
Explanation
West zone descriptions are positive (added) to convert zone time to GMT; east zones are negative (subtracted). The zone description is roughly longitude/15 rounded to the nearest whole hour.
Authority: Bowditch (Pub. No. 9), time and zone description
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