Question 6 — Sunrise and sunset at 35° South — Page 440, Lesson 400

This is the answer key for the "Time" chapter — Questions 6 through 15, plus the Air Almanac extract they're built on. I'll walk you through each worked solution so you can see exactly how the time conversions hang together. Question 6 — Sunrise and sunset at 35° South. We're given SR at 0609 LMT. The arc-to-time conversion for the longitude is 0330 — that's 3 hours 30 minutes. So sunrise in UTC is 0609 plus 0330, giving 0939 UTC. For sunset, we start with 1713 LMT, add the same 0330 arc-to-time, giving 2043 UTC. Then there's a standard time correction of 0300 — that's the zone offset — so sunset in Standard Time is 1743 ST. Notice the pattern: LMT plus arc-to-time gives UTC; UTC plus or minus the zone correction gives Standard Time. Question 7 — Four time answers, all in July. (a) 1100 DST on 4 July. (b) 2200 ST on 4 July. (c) 1600 ST on 4 July. (d) 0400 ST on 5 July. These are the results of converting between Daylight Saving Time, Standard Time, and UTC across the date line — the key is watching whether you cross midnight, which is why (d) lands on the 5th. Question 8 — Three conversions. (a) 0300 UTC on 5 November. (b) 1215 LMT, with arc-to-time of 1139, giving 0036 UTC on 10 July — that's a full day rollover. (c) 2200 on 18 September. Each one is a straightforward LMT-to-UTC or UTC-to-LMT shift using the arc-to-time for the longitude. Question 9 — This is a longitude comparison. Ch.Long. is 124°00'. Arc-to-time gives 08:16. So Kabul is 8 hours 16 minutes FAST on Thule. "Fast on" means Kabul's local time is ahead of Thule's — that's the time difference between the two meridians expressed in clock time. Question 10 — A flight-time problem. Sunset at Rome is 1917 LMT. Arc-to-time is 0050, so sunset in UTC is 1827. At New York, ECT — that's Evening Civil Twilight — is 1942 LMT. Arc-to-time is 0500, so ECT in UTC is 0042. The flight time is from 1827 UTC to 0042 UTC, which is 06 hours 15 minutes. The trick here is that both times are in UTC, so you can subtract directly. Question 11 — A long-haul flight across the date line. Sunrise at Tokyo is 0634 LMT on 14 November. Take-off is 0734 LMT. Arc-to-time is 0920, so take-off in UTC is 2214 on 13 November — note the date goes back a day. Flight time is 0612, so landing is at 0426 UTC on 14 November. Then for Standard Time, the correction is minus 1000, so landing is 1826 ST in Hawaii on 13 November. Again, the date flips because you've crossed the International Date Line. Question 12 — Sunrise is 0355 UTC. Arc-to-time is 0113, so sunrise in LMT is 0508. The latitude is 30 South. This is a reverse lookup — you're given the time and asked to find the latitude where the Sun rises at that LMT. Question 13 — Sunset at South Georgia is 2026 LMT. Arc-to-time is 0229, so sunset in UTC is 2255. The observer's watch is 2 minutes FAST on UTC — meaning the watch reads ahead of UTC, so the actual UTC is 2 minutes behind what the watch shows. Question 14 — Another flight. ECT at Anchorage is 1836 LMT on 25 September. Arc-to-time is plus 0956, giving ECT in UTC as 0432 on 26 September. Then minus 1045 flight time gives 1747 UTC on 25 September — that's take-off. Add 0800 standard time correction, and you get 0147 ST in Hong Kong on 26 September. Watch the date changes carefully here. Question 15 — A longitude conversion. 2020 LMT, minus 1144 arc-to-time for 176° East, gives 0836 UTC on 28 October. Then minus 1152 arc-to-time for 178° West, giving 2044 LMT on 27 October. The date goes back because you've moved from East to West longitude. Now, the Air Almanac extract at the end — this is the table you use to look up sunrise times. The columns are latitudes from N72 down to N10 and the Equator, and the rows are dates in January and February. The numbers are hours and minutes of sunrise in LMT. For example, at N60 on 1 January, sunrise is 0903. At N20 on 1 January, it's 0634. The dashes at high latitudes mean the Sun doesn't rise at all that day — it's polar night. The key skill across all these questions is the same: convert LMT to UTC using arc-to-time, then apply the standard time correction, and always track whether you're crossing midnight or the date line. That's what determines whether the date stays the same or shifts.