Space-Time Singularity -- Solution

		Postulated Jet Aircraft
Categories		Nose	Tail
1	Hemispheres	Southern	Northern
2	Seasons	Summer	Winter
3	Hour of the Day	Midnight	Midnight
4	Day of the Week	Saturday	Friday
5	Date	1st	31st
6	Month	January	December
7	Year	2000	1999
8	Century	21st	20th
9	Millennium	3rd	2nd

eanwhile, Category 3 invokes an explicit assumption: That all time pieces on board the plane are set to the same time. Whereas such might have been the case aboard the SS Warrimoo, it would be unlikely throughout an airliner.

What time is it, anyway?

There's a hint in the puzzle: The navigator aboard the SS Warrimoo used a "star fix" for determining the ship's location. Makes sense. Celestial navigation anywhere in the world requires ascertaining the exact time at the Prime Meridian (0^o longitude). Thus chronometers were set in reference to a clock located in Greenwich England, known back then as Greenwich Mean Time (GMT).

Nota bene, the International Date Line (IDL) crosses the Equator along the Anti-Meridian (180^o longitude), in the Pacific Ocean, exactly opposite the Prime Meridian. Thus, midnight on the IDL occurs at noon GMT.

or avigation, GMT continues to be used as the time reference by pilots and chronometers in cockpits, although the terminology has been recently changed to Coordinated Universal Time, which is officially abbreviated UTC.

All well and good for the flight crew; however, in the passenger compartment, the question (What time is it, anyway?) can comprise quite a range of answers, depending on time zone selections in individual watches and laptops since take-off (smart phones and hand-helds were still rare in 1999). For passengers with time pieces set for anything other than UTC, midnight would not occur at the IDL fly-over. Those passengers would not be in compliance with the table above.

Nota bene, within each time zone, when midnight occurs, the date changes for that time zone. Accordingly, every location within a time zone along the Equator at midnight creates a simple Space-Time Singularity.

What are time zones, anyway?

For legal, commercial, and social activities, people in nearby locations on the globe set their respective clocks to the same time. That has proven to be a good idea. Time zones standardize quantizing of clock settings to hours. The earth rotates 360 / 24 = 15 degrees per hour so the boundaries of time zones might be located on meridians 15 degrees apart. That turns out to be far from ideal.

Sophisticated solvers are invited to study the Standard World Time Zones and confirm the following observations:

Time zones are algebraically numbered, starting at zero for the time zone that is located symmetrically with respect to the Prime Meridian (0^o longitude).
At the Equator, the 0^th time zone is subsumed by the Gulf of Guinea.
On the opposite side of the earth, we find the IDL crossing the Equator at the Anti-Meridian (180^o longitude) in the Pacific Ocean.
Unlike the Prime Meridian, the Anti-Meridian marks the boundary between two time zones (-12 and + 12). Hmm.
Most time zone boundaries that cross the equator are in the oceans, which requires a ship or an airplane to create a Space-Time Singularity.
Time zone boundaries on land often coincide with national borders. Only two of them are along meridians at the equator. They are depicted in this sketch...

ere is the tabulation for two extraordinary Space-Time Singularities...

		Bicycle Wheels
Categories		Front	Rear
1	Hemispheres	Southern	Northern
2	Seasons	Summer	Winter
3	Hour of the Day	Midnight	1:00 AM
4	Day of the Week	Saturday	Friday
5	Date	1st	31st
6	Month	January	December
7	Year	2000	1999
8	Century	21st	20th
9	Millennium	3rd	2nd
Western Hemisphere
10	Country	Brazil	Colombia
11	Time Zone	-4	-5
Eastern Hemisphere
10	Country	Uganda	Congo
11	Time Zone	+2	+1

...which suggests opportunities to establish tourism monuments like this one.

Solvers are invited to find another Space-Time Singularity and submit it here.