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Watch Time The actual time indicated on the chronometer or wrist watch used for navigation, without any corrections. When doing cel nav, the sight time from the watch is recorded to an accuracy of one second at the precise time of the sight. Watch time can be kept on any time zone that is convenient, but should not be changed during a voyage. There is no particular virtue to keeping watch time set to UTC (formerly GMT), since you must correct even this watch time for watch error. You might as well pick a more useful time to carry around on your arm and add this correction as well when you correct for watch error. Also, you need some ship's time that everyone on the boat goes by for watch changes and meals. It is best if this matches your watch time. UTC is very awkward for this purpose. In the end, we do need to figure the GMT of each sight, which we get from UTC = WT ± Watch Error ± Zone Description See: sextant sight, standard time, time zone, universal time, watch error, watch rate, watch time, zone description, and zone time. See also: Time Keeping in Navigation and Weather. Abbreviation:  WT

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