Where are the new days? Date line

At every point on the globe, a new calendar number, otherwise known as a calendar date, begins at midnight. And since midnight occurs at different times in different places on our planet, in some places the new calendar date comes earlier, and in others later. This situation, especially when traveling around the world, previously often led to misunderstandings, expressed in the “loss” or “gain” of an entire day.

For example, the sailors of the flotilla of Ferdinand Magellan (c. 1480–1521), returning in 1522 from a voyage around the world to Spain from the east and stopping in Santiago Bay, discovered a discrepancy of one day between their count of days, which they carefully kept in the ship's register. magazine) and the account kept by local residents, and had to bring church repentance for violating the dates of religious holidays. The secret of such a “loss” is that they traveled around the world in the direction opposite to the rotation of the Earth around its axis. Moving from east to west, when returning to their starting point, the travelers spent one day less on the road (that is, they saw one less sunrise) than the days that had passed at their starting point. (If you travel around the world from west to east, then for travelers it will be one day more than at the starting point. Russian explorers who discovered and developed the west coast of North America, having met with local residents who populated the country from the east, celebrated Sunday on that day , when the locals had Saturday.

The meridian, whose longitude is 180°, or 12 hours, is the boundary on Earth between the western and eastern hemispheres. If from the Greenwich meridian one ship goes east and the other west, then on the first of them, when crossing a meridian with a longitude of 180°, the time will be 12 hours ahead of Greenwich, and on the second - 12 hours behind Greenwich.

Rice. 6. Date line

To avoid confusion in the dates of the month, according to international agreement, it was established date line, which for the most part runs along the meridian with a longitude of 180° (12 hours). This is where the new calendar date (day of the month) begins first. In Fig. Figure 6 shows part of the date line.

The crew of a ship crossing the date line from west to east must count the same day twice so as not to gain in the number of days, and vice versa, when crossing this line from east to west, it is necessary to skip one day so as not to gain This is a waste of a day. Related to this is the problem formulated by Ya. I. Perelman, “How many Fridays are there in February?” For the crew of a ship sailing, for example, between Chukotka and Alaska, there may be ten Fridays in February of a leap year if it passes the international date line at midnight from Friday to Saturday from west to east, and not a single Friday if the ship passes this line at midnight from Thursday to Friday heading west.

It is common to say “Japan is the land of the rising sun.” It is implied that this country is the first to greet the new day. But this is a misconception. In fact, Japan is located approximately 2,750 kilometers from the date line, and cannot in any way be considered the place where the day begins. Even our Chukotka Peninsula is only a few kilometers from this line.

In general, the date line is a rather curious marking. In astronomical terms, it clearly passes along the 180th meridian. But due to the fact that thousands of islands are scattered in the Pacific Ocean, many of which lie within the 180th meridian and sometimes even belong to the same state, they decided to break the line and adapt it to the needs of humanity. It is extremely illogical if in one part of the island it is still “today”, and in another it is already “tomorrow”. Formally, the date line now looks like this.

Fiji includes the island of Taveuni, through which (almost in the middle) the 180th meridian passes, so the island can safely be considered the place where “today” meets “tomorrow”. Moreover, if in the western part of the island it is Monday, then in the eastern part it is already Tuesday.

Taveuni Island and the date line on the map

• Geographic coordinates of the island -16.857214, -179.970951
• The distance from the capital of Fiji, Suva is approximately 220 km
• In the northernmost part of the island there is its own Matei airport, 18 kilometers from the 180th meridian

And although formally the date line has been moved far beyond the island, there is an interesting attraction on Taveuni. A place where the past meets the future.

This is, of course, not a grandiose world attraction, but, you see, where else can a person have one foot in the passing day, and the other in the coming one.

As can be seen in the photographs, the landmark changed its appearance at different times. One thing remained the same - location.

And even though you, most likely, will not be amazed by its appearance, the very fact of being there, let’s not be afraid of this word, “at the edge of the Earth,” and even in two days at the same time, will probably be remembered for a lifetime. Moreover, you can easily jump from one day to another and back.

It's a very unusual feeling when you cross the International Date Line in the air and look at route on the monitor screen on the plane. My friend and I took off from New Zealand at 5 pm, but they arrived in Tahiti ten minutes before midnight, but, as it turned out, the previous day. It turned out kind of "Groundhog Day" when we lived the same day twice. And on the way back we took off at 9 am and arrived at two o’clock, but the next day. One day was lost that is, it was not on our calendar. I can’t even imagine how the flight attendants who constantly fly this route cope with such confusion of dates.

Winding date line

Roughly speaking, the line, to the west and east of which there are different dates, runs along the meridian 180 degrees. In fact, there is no international agreement that in any way regulates the passage of this line. There is a concept maritime date line, which was installed in London, at the Anglo-French conference in June 1917, and which adopted the terrestrial time zone system. Subsequently, these standards for navigation purposes were adopted all maritime powers. Unlike maritime rules, geographic time and date are on their own land territory and in their Each state establishes its territorial waters independently. For example, the 180 degree meridian passes through the territory of the Russian Wrangel Island and divides it in half. Obviously, it is inconvenient for a state, even with several time zones, to introduce different dates on its territory. That's why the date line does not pass strictly along the meridian, but wears quirky character. It does not pass anywhere on land except Antarctica.

Starting from North Pole, the line deviates from the meridian:

• in the area Wrangel Islands and passing through Bering Strait;
• going around Aleutian Islands from the west;
• south of the equator, going significantly east, towards Kiribati;
• passing east of Tonga and New Zealand.

After this, the international date line returns to the 180 degree meridian and connects with South Pole.

Changeable Date Line

Some interesting facts about the date change:

• after 1844 back to Asian date, although before that they lived according to the American one;
• in 1892 Samoa changed date for the convenience of trading with, and in 2011 came back, to the east, when trade relations with Australia and New Zealand came to the fore;
• , after sale, switched to American date, although it was previously synchronized with Russia;
• until 1995, Kiribati was divided into two time zones and then returned to one zone, west of the date line.

Returning to our flight from New Zealand to Tahiti, the date line must be taken into account when hotel reservations. We were flying out on Friday the 2nd, and booked a hotel from Thursday the 1st to Friday, had to twice. First time in Auckland on the eve of departure, and for the second time already in Tahiti, according to I'll arrive. The change of dates must be taken into account, otherwise it happens that people find themselves in an unpleasant situation, left without an overnight stay due to carelessness double booking.

When counting time by calendar days, it is necessary to agree where (on which meridian) the new date (day of the month) begins.

According to international agreement, the date line (demarcation line) runs for the most part along the meridian 180° away from Greenwich, retreating from it to the west - near the Wrangel and Aleutian islands, to the east - near the tip of Asia, the islands of Fiji, Samoa, Tongatabu , Kermadec and Chatham. The need to establish a date line is caused by the following considerations.

When traveling around the world from west to east, the traveler passes points where the local (or zone) time clock shows an increasingly advanced time compared to the local (zone) time of the traveler's point of departure. Gradually moving the hands of his watch forward, by the end of his trip around the world, the traveler counts

one extra day. And vice versa, when traveling around the world from east to west, one day is lost.

To avoid the associated errors in counting days, a date line was installed.

West of the date line, the day of the month is always one more than east of it. Therefore, after crossing this line from west to east, it is necessary to reduce the calendar number, and after crossing it from east to west, on the contrary, increase it by one. For example, if a ship crosses the demarcation line on November 8, going from west to east, then on the ship the date at midnight following crossing this line does not change, that is, two days in a row are dated as November 8. And vice versa, if a ship crosses this line on November 8, going from east to west, then at midnight following crossing it, the date changes immediately to November 10, and there will be no day with the name November 9 on the ship.

Compliance with this rule eliminates the mistake in counting days, first made by the participants of Magellan’s first round-the-world expedition in the 16th century, when they returned to their homeland and discovered that they differed in counting the days and numbers of the month from the inhabitants who remained in place by exactly one day.

Time

5.1 Local time and longitude. The time measured on a given geographical meridian is called the local time of that meridian.

For all places on the same meridian, the hour angle of the vernal equinox (or the Sun, or the mean sun) is at any moment the same. Therefore, throughout the entire geographic meridian, local time (sidereal or solar) is the same at the same moment.

If the difference in geographical longitude of two places is Dl, then in a more eastern place the hour angle of any star will be Dl greater than the hour angle of the same star in a more western place. Therefore the difference

any local times on two meridians at the same physical moment is always equal to the difference in the longitudes of these meridians, expressed in hourly measure (in time units).

Directly from astronomical observations, the local time of the meridian on which these observations were made is obtained.

Universal time. The local mean solar time of the Greenwich (prime) meridian is called universal time T0.

Assuming in formula (1.26) Tm2 = T0 and l 2 = 0, Tm1 = Tm and l 1 = l, we obtain:

Tm = T0 + l ,(1.27)

those. the local mean time of any point on Earth is always equal to universal time at that moment plus the longitude of that point, expressed in hourly units and considered positive east of Greenwich.

In astronomical calendars, the moments of most phenomena are indicated by universal time T0. The moments of these phenomena according to local time Tt. are easily determined by the formula.

5.2 Standard time. In everyday life, using both local mean solar time and universal time is inconvenient. The first is because there are, in principle, as many local time counting systems as there are

geographical meridians, i.e. countless. Therefore, in order to establish the sequence of events or phenomena noted in local time, it is absolutely necessary to know, in addition to the moments, also the difference in longitude of those meridians on which these events or phenomena took place. The sequence of events marked in universal time is easily established, but there is a big difference between universal time and the local time of meridians distant from

Greenwich time over significant distances creates inconvenience when using universal time in everyday life.

In 1884, a belt system for counting average time was proposed, the essence of which is as follows. Time is counted only on 24 main geographical meridians, located from each other in longitude exactly 15° (or 1h), approximately in the middle of each time zone. Time zones are the areas of the earth's surface into which it is conventionally divided by lines running from its north pole to the south and spaced approximately 7°.5 from the main meridians. These lines, or boundaries of time zones, accurately follow geographic meridians only in open seas and oceans and in uninhabited land areas. For the rest of their length, they follow state, administrative, economic or geographical boundaries, retreating from the corresponding meridian in one direction or another. Time zones are numbered from 0 to 23. Greenwich is taken as the main meridian of the zero zone.

The main meridian of the first time zone is located exactly 15° east of Greenwich, the second - 30°, the third - 45°, etc.

to the 23rd time zone, the main meridian of which has an east longitude from Greenwich of 345° (or a west longitude of 15°).

The local mean solar time of the main meridian of any time zone is called standard time Tp, according to which

keeping track of time throughout the entire territory lying in a given time zone. The difference between the local time Tm of any point and its standard time Tp based on the last equation is equal to

Tm - Tn = l - ph, (1.28)

where l is the eastern longitude of the point from Greenwich, and nh is the number of integer hours equal to the number of the time zone in which the point is located (longitude of the main meridian of the time zone).

Since the boundaries of time zones are approximately 7°.5 away from the main meridians, the difference (Tm - Tn) may be slightly larger or slightly smaller; 30m only for points located near the boundaries of time zones.

The standard time of a given zone is related to universal time by an obvious relationship

Tn = T0 + nh.(1.29)

It is also quite obvious that the difference between the zone times of two points is an integer number of hours equal to the difference in the numbers of their time zones.

In the USSR, standard time was introduced on July 1, 1919. Due to significantly changed conditions of the country's economic development, the boundaries of time zones on the territory of the USSR were revised on December 1, 1956.