Time Zones
Remember, for Time Zones: add EAST; subtract WEST
Which means, as you move East, add one hour per time zone. As you move West, subtract one hour per time zone.
BUT at the International Date Line do the opposite:
add 1 day WEST; subtract 1 day EAST
TZ → add East; IDL → add West
As the world shrinks, knowledge of Time Zones become more and fundamental to our lives. While Aunt Mabel in Australia might love a video chat with you, reaching her at 4 in the morning, may not be the best time!
Before railways, time zones weren't needed. But, by the mid-19th century, with intercontinental telecommunications on the horizon, they became essential. In 1879, Scottish-born Canadian Sir Sanford Fleming first advocated a universal co-ordinated time with 24 1-hour time zones, set 15° apart. His system was officially adopted in 1884 with 0° longitude set at Greenwich, England and the International Date Line set at the anti-meridian of 180°. From there, it was up to each individual country to adopt time zones appropriate to their location.
Understanding Time Zones (Gedge: 4:16)
Why are Time Zones so Weird?
(MinuteEarth 2:14)
Strangest Time Zones of the World (WonderWhy: 8:38)
Samoa skips a Friday and goes back to the future side of dateline (The Guardian article + video 1:20)
Give us our eleven days! The calendar riots of 1752
(Historic UK)
Time has no meaning at the North Pole (Scientific American)
20 Vetted Tools and Tips for Managing Time Zone Differences (I Done This)