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Calculating LMT, UTC and Local Standard Time

Refer to AIP GEN 2.7 Daylight / Darkness Graphs to compute the beginning or end of daylight using the graphs and table contained in this section:

  1. enter the top or bottom of the scale al the appropriate date
  2. move vertically up or down to the curve for the latitude of the place concerned (interpolating for intermediate latitudes if necessary)
  3. move horizontally to the left a right and read local mean time on the vertical scale at the side
  4. to convert to UTC, subtract (in E longitudes) from the LMT obtained, the time increment corresponding to the longitude of the place concerned in the "Conversion of Am to Time" table.
  • to convert to EST, add 10 hours to UTC
  • to convert to CST add 91/2 hours to UTC
  • to convert m WST add 8 hours to UTC

Find the End of Daylight for Echoca (S36 09.0 E144 48.0) on the 20th November.

Using the graph, enter al 20th November at the top of the page and follow downwards to latitude 36" (by interpolation), then horizontally to the left and read off LMT=1920. To convert to UTC, enter the 'Conversion of Am to Time" table, at longitude 144' (9 hours 36 minutes). Add the increment corresponding to 46' in the right hand column.

  1. Local Mean Time found on the EOD graph: 1920 LMT.
  2. Conversion of Arc to Time from the table: 3' 04" + 0936 = 0939.
  3. Subtract the Arc to Time from the LMT to find UTC: 1920 - 0939 = 0941 UTC.
  4. To find EST add 10 hours to UTC: 0941 + 10 = 1941 EST.