So we start with Standard Time Vancouver, 5th, 00 hours 08 minutes — Page 408, Lesson 362

We're moving into a new set of worked examples now, and these are the real meat of time conversion. Let's work through them one by one, because each one shows you a slightly different trap. Example 2 — Find the LMT in Vancouver, Canada, at longitude 123°W, if the Standard Time is 0008 hours on 5th March. So we start with Standard Time Vancouver, 5th, 00 hours 08 minutes. The Standard Time Difference is plus 8 hours — that's from List 3 in the Air Almanac. Adding that gives us UTC, 5th, 08 hours 08 minutes. Now we convert to LMT. Vancouver is west, so we subtract the arc/time for longitude 123°W, which is 8 hours 12 minutes. That gives us LMT Vancouver, 4th, 23 hours 56 minutes. Notice the date went back to the 4th — that's the key thing to watch. Example 3 — Now we go the other way. Find the Standard Time in Fairbanks, Alaska, at 148°W, if the LMT is 0614 on 18th February. We start with LMT Fairbanks, 18th, 06 hours 14 minutes. Since Fairbanks is west, we add the arc/time for 148°W, which is 9 hours 52 minutes — that's the "UTC BEST" rule. That gives us UTC, 18th, 16 hours 06 minutes. Then we subtract the Standard Time Difference for Fairbanks, which is minus 9 hours from List 3. That gives us Standard Time Fairbanks, 18th, 07 hours 06 minutes. Example 4 — This one crosses hemispheres. Find the Standard Time in Georgetown, Guyana, at 08°N 060°W, when the LMT in Sydney, New South Wales, at 151°20'E, is 1116 on 21st January. Start with LMT Sydney, 21st, 11 hours 16 minutes. Sydney is east, so we subtract the arc/time for 151°20'E, which is 10 hours 05 minutes — that's "UTC LEAST." That gives us UTC, 21st, 01 hour 11 minutes. Then we subtract the Standard Time Difference for Guyana, which is minus 3 hours from List 3. That gives us Standard Time Georgetown, 20th, 22 hours 11 minutes. Again, the date rolled back to the 20th. Example 5 — Now we have an aircraft in flight. An aircraft left position A at longitude 164°W on a westerly heading at 2200 hours LMT on 3rd May. We need the LMT and local date of arrival at position B at 173°E, with a flight time of 6 hours. Start with Depart A, 3rd, 22 hours 00 minutes. A is west, so we add the arc/time for 164°W, which is 10 hours 56 minutes — "UTC BEST." That gives us Depart A in UTC, 4th, 08 hours 56 minutes. Add the flight time of 6 hours, giving Arrive B in UTC, 4th, 14 hours 56 minutes. Now B is east, so we add the arc/time for 173°E, which is 11 hours 32 minutes. That gives us Arrive B, 5th, 02 hours 28 minutes. The date jumped forward to the 5th. Example 6 — The reverse. An aircraft left position X at 175°E on an easterly heading at 0100 hours LMT on 18th November. We need arrival at Y at 150°W, flight time 4 hours. Start with Depart X, 18th, 01 hour 00 minutes. X is east, so we subtract the arc/time for 175°E, which is 11 hours 40 minutes — "UTC LEAST." That gives us Depart X in UTC, 17th, 13 hours 20 minutes. Add the 4-hour flight time, giving Arrive Y in UTC, 17th, 17 hours 20 minutes. Now Y is west, so we subtract the arc/time for 150°W, which is 10 hours 00 minutes. That gives us Arrive Y, 17th, 07 hours 20 minutes. Now let me give you the Summary that ties all this together, because this is the part you'll want to memorise. LMT is based on the movement of the mean Sun, which travels through 15° of longitude per hour. UTC is simply the LMT on the Greenwich Meridian — that's the definition. The difference in LMT at two places is found by finding the difference in their longitudes and converting it into time at the rate of 15° per hour. But there's an exception: where the shorter longitudinal arc spans the date line, you must work through UTC instead. And be prepared to calculate the time equivalent of longitude without using the Air Almanac — you need to be able to do that conversion in your head or on paper. Zone Time is in the EASA syllabus. Be prepared to convert longitude into zone number, and to convert between Zone Time and UTC. Standard Time is used to prevent the extreme inconvenience of using LMT on clocks — that's the whole reason it exists. Standard Time Differences for all countries are found in Lists 1, 2 and 3 in the Air Almanac. Conversion of LMT to Standard Time, or vice versa, is best done through UTC. And LMT problems involving an aircraft crossing the International Date Line are also best done through UTC. So the golden rule throughout all six examples: whenever you cross the date line, or whenever you're converting between LMT and Standard Time, always route through UTC. That's the safe path that keeps your dates correct.