UTC in the context of "Babylonian calendar"

The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the Solar System as Earth's North Pole.

Due to Earth's axial tilt of 23.439281°, there is a seasonal variation in the lengths of the day and night. There is also a seasonal variation in temperatures, which lags the variation in day and night. Conventionally, winter in the Northern Hemisphere is taken as the period from the December solstice (typically December 21 UTC) to the March equinox (typically March 20 UTC), while summer is taken as the period from the June solstice through to the September equinox (typically on 23 September UTC). The dates vary each year due to the difference between the calendar year and the astronomical year. Within the Northern Hemisphere, oceanic currents can change the weather patterns that affect many factors within the north coast. Such events include El Niño–Southern Oscillation.

Apollo 11 was the first spaceflight to land humans on the Moon, conducted by NASA from July 16 to 24, 1969. Commander Neil Armstrong and Lunar Module Pilot Edwin "Buzz" Aldrin landed the Lunar Module Eagle on July 20 at 20:17 UTC, and Armstrong became the first person to step onto the surface about six hours later, at 02:56 UTC on July 21. Aldrin joined him 19 minutes afterward, and together they spent about two and a half hours exploring the site they had named Tranquility Base upon landing. They collected 47.5 pounds (21.5 kg) of lunar material to bring back to Earth before re-entering the Lunar Module. In total, they were on the Moon’s surface for 21 hours, 36 minutes before returning to the Command Module Columbia, which remained in lunar orbit, piloted by Michael Collins.

Apollo 11 was launched by a Saturn V rocket from Kennedy Space Center in Florida, on July 16 at 13:32 UTC (9:32 am EDT, local time). It was the fifth crewed mission of the Apollo program. The Apollo spacecraft consisted of three parts: the command module (CM), which housed the three astronauts and was the only part to return to Earth; the service module (SM), which provided propulsion, electrical power, oxygen, and water to the command module; and the Lunar Module (LM), which had two stages—a descent stage with a large engine and fuel tanks for landing on the Moon, and a lighter ascent stage containing a cabin for two astronauts and a small engine to return them to lunar orbit.

Moscow Time (MSK; Russian: моско́вское вре́мя, romanized: moskovskoye vremya) is the time zone for the city of Moscow, Russia, and most of western Russia, including Saint Petersburg. It is the second-westernmost of the eleven time zones of Russia, after the non-continguous Kaliningrad enclave. It has been set to UTC+03:00 without DST since 26 October 2014; before that date it had been set to UTC+04:00 year-round on 27 March 2011.

Moscow Time is used to schedule trains (until 1 August 2018), ships, etc. throughout Russia, but air transport in Russia is scheduled using local time. Since 1 August 2018, Russian railways switched to using local time. Time in Russia is often announced throughout the country's other timezones on radio stations as Moscow Time, which is also registered in telegrams, etc. Descriptions of time zones in Russia are often based on Moscow Time rather than UTC; for example, Yakutsk (UTC+09:00) is said to be MSK+6 in Russia.

Yekaterinburg Time (YEKT) is the time zone five hours ahead of UTC (UTC+05:00) and 2 hours ahead of Moscow Time (MSK+2).

In 2011, Russia moved to year-round daylight saving time. Instead of switching between UTC+05:00 in winter and UTC+06:00 in summer, Yekaterinburg time was set to UTC+06:00 until 2014, when it was reset back to UTC+05:00 year-round.

Omsk Time (OMST) is a time zone in Russia that is six hours ahead of UTC (UTC+06:00), and 3 hours ahead of Moscow Time (MSK). It is used in Omsk Oblast.

Krasnoyarsk Time (KRAT) is the time zone seven hours ahead of UTC (UTC+07:00) and 4 hours ahead of Moscow Time (MSK+4). KRAT is the official time zone for central and east Siberian regions of Krasnoyarsk Krai, Kemerovo Oblast, Khakassia and Tuva.

Novosibirsk Oblast used this time zone until 1993, when it was known as Novosibirsk Time (NOVT/NOVST). The Russian government renamed the time zone shortly after Novosibirsk opted for another time zone instead.

Irkutsk Time (IRKT) is the time zone eight hours ahead of UTC (UTC+08:00) and 5 hours ahead of Moscow Time (MSK+5).

The time zone covers Buryatia and Irkutsk Oblast.

In March 1980, a series of volcanic explosions and pyroclastic flows began at Mount St. Helens in Skamania County, Washington, United States. A series of phreatic blasts occurred from the summit and escalated for nearly two months until a catastrophic, major explosive eruption took place on May 18, 1980, at 8:32 a.m. The eruption, which had a volcanic explosivity index of 5, was the first to occur in the contiguous United States since the much smaller 1915 eruption of Lassen Peak in California. It has often been considered the most disastrous volcanic eruption in U.S. history.

The eruption was preceded by a series of earthquakes and steam-venting episodes caused by an injection of magma at shallow depth below the volcano that created a large bulge and a fracture system on the mountain's north slope. An earthquake at 8:32:11 am PDT (UTC−7) on May 18, 1980, caused the entire weakened north face to slide away, a sector collapse which was the largest subaerial landslide in recorded history. This allowed the partly molten rock, rich in high-pressure gas and steam, to suddenly explode northward toward Spirit Lake in a hot mix of lava and pulverized older rock, overtaking the landslide. An eruption column rose 80,000 feet (24 km; 15 mi) into the atmosphere and deposited ash in eleven U.S. states and various Canadian provinces. At the same time, snow, ice, and several entire glaciers on the volcano melted, forming a series of large lahars (volcanic mudslides) that reached as far as the Columbia River, nearly 50 miles (80 km; 260,000 ft) to the southwest. Less severe outbursts continued into the next day, only to be followed by other large, but not as destructive, eruptions later that year. The thermal energy released during the eruption was equal to 26 megatons of TNT.