73

Why? Because there was no point. First, according to more modern astronomical measurements, the current length of the year is closer to about 365.2422 days, so they would've been relatively less accurate had they used a more precise value of 365.2425463 days per year. Which leads to a very important point about math: you need to be very mindful about how ...


64

The concept of longitude was first developed by ancient Greek astronomers. Hipparchus (2nd century BCE) used a coordinate system that assumed a spherical earth, and divided it into 360° as we still do today. His prime meridian passed through Alexandria. He also proposed a method of determining longitude by comparing the local time of a lunar eclipse at two ...


29

Time zones were not discovered, they were defined. Without time zones, you have the concept of solar noon. A time zone is an area where the solar noon of a central place (like a royal observatory) is applied in a wider area. This became relevant with railway timetables. A train leaves at 12:00, travels for 60 minutes, and the clock at the destination should ...


19

The Gregorian Calendar was introduced (to the Catholic World) in 1582, the result of preparation over the preceding five or so years. However the popularization of decimal fractions would wait another three years until the publication of La Thiende [The Tenth] in 1585 by the Flemish mathematician Simon Stevin. Though not the inventor of a decimal ...


11

I point out that the survivors of the Magellan expedition were startled by a date discrepancy. Twenty crewmen died of starvation by 9 July 1522, when Elcano put into Portuguese Cape Verde for provisions. The crew was surprised to learn that the date was actually 10 July 1522,[104] as they had recorded every day of the three-year journey without omission. ...


10

There is no recorded moment, but the time difference in places with different longitude was discovered as soon as people realized that the Earth is round, and that Sun rotates about it (or vice versa, which does not matter for this question). We do not know when exactly did this happen, since almost all astronomic and geographic literature from the ancient ...


6

None of those watches are worth anything, they are all quartz watches with generic movements. Each one could be bought on ebay for less than 10 dollars.


4

The existing answers are good, but I would add one additional detail, building on your concept of "future-proofing": The exercise of reforming a calendar was intended to make a calendar more accurate, but was not intended to eliminate the need for any theoretical future adjustment. The Gregorian reform was inspired by the Julian reform, and the ...


3

The other answers have touched some very good points, but there is a mathematical point I would like to make as well: The way the leap year rules are designed is fundamentally incompatible with the decimal expansion. Specifically, rules of the kind "leap/no leap year every X years" don't really care about the number of digits, they are more of a ...


3

Having weeks of seven days is a direct consequence of the lunar cycle. Each 29 day lunar cycle comprises four equal phases of 7.25 days long each. Starting from New Moon: Waxing crescent ending in First Quarter; Waxing gibbous ending in Full Moon; Waning gibbous ending in Third Quarter; and finally Waning crescent ending in New Moon. These seven and a ...


1

Where did the idea of weeks originate and why do they have seven days? The idea of weeks, not necessarily seven days in length, originated independently, across many cultures, and at various times, ultimately for purely utilitarian reasons, such as having a practical, medium-sized time unit, between a day (which is oftentimes too short) and a month (which ...


1

In 1928 the Beiyang government was overthrown by the KMT. The KMT moved the capital to Nanking along with central observatory duties. Shanghai remained in the Central Plain time zone whose clock provider was still Zikawei (or Sicawei), the only change at the time I can find is that the Beijing Mean Solar Time was replaced by the Central Plain time for ...


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