Instruct: Given a question, retrieve relevant passages that can help answer the question.
Query: When is the next leap year?
The name "leap year" probably comes from the fact that while a fixed date in the Gregorian calendar normally advances one day of the week from one year to the next, the day of the week in the 12 months following the leap day (from March 1 through February 28 of the following year) will advance two days due to the extra day (thus "leaping over" one of the days in the week).[2][3] For example, Christmas Day (December 25) fell on a Sunday in 2016, and Monday in 2017, then it fell on Tuesday in 2018, and will fall on Wednesday in 2019 but then "leaps" over Thursday to fall on a Friday in 2020.
Older Trimble GPS receivers had a software flaw that would insert a leap second immediately after the GPS constellation started broadcasting the next leap second insertion time (some months in advance of the actual leap second), rather than waiting for the next leap second to happen. This left the receiver's time off by a second in the interim.
The Buddhist and Hebrew calendars restrict the leap month to a single month of the year; the number of common months between leap months is, therefore, usually 36, but occasionally only 24 months. Because the Chinese and Hindu lunisolar calendars allow the leap month to occur after or before (respectively) any month but use the true motion of the sun, their leap months do not usually occur within a couple of months of perihelion, when the apparent speed of the sun along the ecliptic is fastest (now about 3 January). This increases the usual number of common months between leap months to roughly 34 months when a doublet of common years occurs, while reducing the number to about 29 months when only a common singleton occurs.
The reform was adopted initially by the Catholic countries of Europe and their overseas possessions. Over the next three centuries, the Protestant and Eastern Orthodox countries also moved to what they called the "Improved calendar", with Greece being the last European country to adopt the calendar in 1923. To unambiguously specify a date during the transition period, dual dating is sometimes used to specify both Old Style and New Style dates. Due to globalization in the 20th century, the calendar has also been adopted by most non-Western countries for civil purposes. The calendar era carries the alternative secular name of "Common Era".
The Gregorian calendar is a solar calendar with 12 months of 28–31 days each. A regular Gregorian year consists of 365 days, but in certain years known as leap years, a leap day is added to February. Gregorian years are identified by consecutive year numbers. A calendar date is fully specified by the year (numbered according to a calendar era, in this case "Anno Domini" or Common Era), the month (identified by name or number), and the day of the month (numbered sequentially starting from 1). Although the calendar year currently runs from 1 January to 31 December, at previous times year numbers were based on a different starting point within the calendar (see the "beginning of the year" section below).
In the Julian calendar, a leap year occurred every 4 years, and the leap day was inserted by doubling 24 February. The Gregorian reform omitted a leap day in three of every 400 years and left the leap day unchanged. However, it has become customary in the modern period to number the days sequentially with no gaps, and 29 February is typically considered as the leap day. Before the 1969 revision of the Roman Calendar, the Roman Catholic Church delayed February feasts after the 23rd by one day in leap years; Masses celebrated according to the previous calendar still reflect this delay.
According to the tropical system of astrology, the Sun enters the sign of Aries when it reaches the March equinox, which occurs on average on March 20 (by design). Because the Earth takes approximately 365.24 days to go around the Sun, the precise time of the equinox is not the same each year, and generally will occur about six hours later from one year to the next until reset by a leap year. February 29 of a leap year causes that year's vernal equinox to fall about eighteen hours earlier compared with the previous year. From 1800 to 2050 inclusive the vernal equinox date has (or will) range(d) from March 19 at 22:34 UT1 in 2048 to March 21 at 19:15 UT1 in 1903. 
Century leap year Calendar reform includes proposals that have not (yet) been adopted. Leap second Leap week calendar Leap year bug Sansculottides Summer Olympic Games – which have been held in each leap year since 1896 (and also in 1900, which was not a leap year) UEFA European Championship – which have been held in each leap year since 1960 Zeller's congruence
The Indian national calendar starts the year on the day next to the vernal equinox on 22 March (21 March in leap years) with a 30-day month (31 days in leap years), then has 5 months of 31 days followed by 6 months of 30 days.
Within each 100-year block, the cyclic nature of the Gregorian calendar proceeds in exactly the same fashion as its Julian predecessor: A common year begins and ends on the same day of the week, so the following year will begin on the next successive day of the week. A leap year has one more day, so the year following a leap year begins on the "second" day of the week after the leap year began. Every four years, the starting weekday advances five days, so over a 28-year period it advances 35, returning to the same place in both the leap year progression and the starting weekday. This cycle completes three times in 84 years, leaving 16 years in the fourth, incomplete cycle of the century.
As a consequence, 19 April is the date on which Easter falls most frequently in the Gregorian calendar: in about 3.87% of the years. 22 March is the least frequent, with 0.48%.
The relation between lunar and solar calendar dates is made independent of the leap day scheme for the solar year. Basically the Gregorian calendar still uses the Julian calendar with a leap day every four years, so a Metonic cycle of 19 years has 6,940 or 6,939 days with five or four leap days. Now the lunar cycle counts only days. By not labeling and counting the leap day with an epact number, but having the next new moon fall on the same calendar date as without the leap day, the current lunation gets extended by a day, and the 235 lunations cover as many days as the 19 years. So the burden of synchronizing the calendar with the moon (intermediate-term accuracy) is shifted to the solar calendar, which may use any suitable intercalation scheme; all under the assumption that 19 solar years = 235 lunations (long-term inaccuracy). A consequence is that the reckoned age of the moon may be off by a day, and also that the lunations that contain the leap day may be 31 days long, which would never happen if the real moon were followed (short-term inaccuracies). This is the price for a regular fit to the solar calendar.
Dusky dolphins perform a number of aerial displays, including leaps, backslaps, headslaps, tailslaps, spins, and noseouts. They also perform head-over-tail leaps which have been called the most "acrobatic" of the displays. A headfirst re-entry is performed when a dolphin leaps entirely out of the water and positions its back in a curve while it flips the tail to land back in the water head-first. "Humping" is similar, except the snout and tail remain in the water when the dolphin is the arch. Leaps, head-over-tail leaps, backslaps, headslaps, tailslaps, and spins are often done over and over again. Young dusky dolphins apparently are not born with the ability to perform the leaps and must learn to master each one. Calves appear to learn the leaps in this order: noisy leaps, head first re-entries, coordinated leaps, and acrobatic leaps. Adults may perform different leaps in different contexts, and calves may independently learn how to perform leaps, as well as learn when to perform these when interacting others.
Ash Wednesday is exactly 46 days before Easter Sunday, a moveable feast based on the cycles of the moon. The earliest date Ash Wednesday can occur is 4 February (which is only possible during a common year with Easter on 22 March), which happened in 1598, 1693, 1761 and 1818 and will next occur in 2285. The latest date Ash Wednesday can occur is 10 March (when Easter Day falls on 25 April) which occurred in 1666, 1734, 1886 and 1943 and will next occur in 2038. Ash Wednesday has never occurred on Leap Year Day (29 February), and it will not occur as such until 2096. The only other years of the third millennium that will have Ash Wednesday on 29 February are 2468, 2688, 2840 and 2992. (Ash Wednesday falls on 29 February only if Easter is on 15 April in a leap year starting on a Sunday.)
There are times when a common year is 353 days, or a leap year is 383 days; these are called the Defective Years. When a common year is 355 days, or a leap year is 385 days, these are called the Excessive Years. In Defective years, the regularly 30-day Kislev is made 29 days; in Excessive Years, the regularly 29-day Heshvan is made 30 days.
A simple rule for determining whether a year is a leap year has been given above. However, there is another rule which not only tells whether the year is leap but also gives the fraction of a month by which the calendar is behind the seasons, useful for agricultural purposes. To determine whether year "n" of the calendar is a leap year, find the remainder on dividing [(7 × "n") + 1] by 19. If the remainder is 6 or less it is a leap year; if it is 7 or more it is not. For example, the The This works because as there are seven leap years in nineteen years the difference between the solar and lunar years increases by 7/19-month per year. When the difference goes above 18/19-month this signifies a leap year, and the difference is reduced by one month.
Egyptian scholars were involved with the establishment of Julius Caesar's reform of the Roman calendar, although the Roman priests initially misapplied its formula and—by counting inclusively—added leap days every three years instead of every four. The mistake was corrected by Augustus through omitting leap years for a number of cycles until 4. As the personal ruler of Egypt, he also imposed a reform of its calendar in 26 or 25, possibly to correspond with the beginning of a new Callipic cycle, with the first leap day occurring on 6 Epag. in the year 22. This "Alexandrian calendar" corresponds almost exactly to the Julian, causing 1Thoth to remain at 29August except during the year before a Julian leap year, when it occurs on 30August instead. The calendars then resume their correspondence after 4Phamenoth/ 29February of the next year.
Instead of changing from the Julian calendar to the Gregorian calendar by omitting a block of consecutive days, as had been done in other countries, the Swedish Empire planned to change gradually by omitting all leap days from 1700 to 1740, inclusive. Although the leap day was omitted in February 1700, the Great Northern War began later that year, diverting the attention of the Swedes from their calendar so that they did not omit leap days on the next two occasions; 1704 and 1708 remained leap years.
Jews read it the 22nd Sabbath after Simchat Torah, generally in March or rarely in late February. The lunisolar Hebrew calendar contains up to 55 weeks, the exact number varying between 50 in common years and 54 or 55 in leap years. In leap years (for example, 2019, 2022, 2024, and 2027), parashah Vayakhel is read separately. In common years (for example, 2017, 2018, 2020, 2021, 2023, and 2026), parashah Vayakhel is usually combined with the next parashah, Pekudei, to help achieve the number of weekly readings needed (although in some non-leap years, such as 2025, they are not combined).
Normally, a year is a leap year if it is evenly divisible by four. A year divisible by 100, however, is not a leap year in the Gregorian calendar unless it is also divisible by 400. For example, 1600 was a leap year, but 1700, 1800 and 1900 were not. Some programs may have relied on the oversimplified rule that "a year divisible by four is a leap year". This method works fine for the year 2000 (because it is a leap year), and will not become a problem until 2100, when older legacy programs will likely have long since been replaced. Other programs contained incorrect leap year logic, assuming for instance that no year divisible by 100 could be a leap year. An assessment of this "leap year problem" including a number of real life code fragments appeared in 1998. For information on why century years are treated differently, see Gregorian calendar.
When a leap second occurs, the UTC day is not exactly seconds long and the Unix time number (which always increases by exactly each day) experiences a discontinuity. At the end of a day with a negative leap second, which has not yet occurred, the Unix time number would jump up by 1 to the start of the next day. During a positive leap second at the end of a day, which occurs about every year and a half on average, the Unix time number increases continuously into the next day during the leap second and then at the end of the leap second jumps back by 1 (returning to the start of the next day). For example, this is what happened on strictly conforming POSIX.1 systems at the end of 1998:
For Julian dates before 1300 and after 1999, the year in the table that differs by an exact multiple of 700 years is used. For Gregorian dates after 2299,the year in the table that differs by an exact multiple of 400 years is used. The values "" through "" indicate the remainder when the Hundreds value is divided by 7 and 4 respectively, indicating how the series extend in either direction. Both Julian and Gregorian values are shown 1500–1999 for convenience. Bold figures (e.g., 04) denote leap year. If a year ends in 00 and its hundreds are in bold it is a leap year. Thus 19 indicates that 1900 is not a Gregorian leap year, (but 19 in the Julian column indicates that it "is" a Julian leap year, as are all Julian "x"00 years). 20 indicates that 2000 is a leap year. Use Jan and Feb only in leap years.
Technically, a leapling will have fewer birthday anniversaries than their age in years. This phenomenon is exploited when a person claims to be only a quarter of their actual age, by counting their leap-year birthday anniversaries only: for example, in Gilbert and Sullivan's 1879 comic opera The Pirates of Penzance, Frederic the pirate apprentice discovers that he is bound to serve the pirates until his 21st birthday (that is, when he turns 88 years old, since 1900 was not a leap year) rather than until his 21st year.
This date correspondence applies for the Gregorian years 1900 to 2099. The Ethiopian leap year is every four without exception, while Gregorian centurial years are only leap years when exactly divisible by 400; thus a set of corresponding dates will most often apply for a single century. As the Gregorian year 2000 is a leap year, the current correspondence lasts two centuries instead.
The 24th century of the Anno Domini (common era) will begin on January 1, 2301 and end on December 31, 2400 of the Gregorian calendar. Unlike most century years, the year 2400 will be a leap year, and the next century leap year in the Gregorian calendar after 2000."", "", and "", as well as "Star Trek Generations", "", "", and "" are set in the 24th century.
The 28th century of the anno Domini (common) will begin on January 1, 2701 and end on December 31, 2800 of the Gregorian calendar. Unlike most century years, the year 2800 will be a leap year, and the next century leap year after 2400.
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A leap year starting on Saturday is any year with 366 days (i.e. it includes 29 February) that begins on Saturday, 1 January, and ends on Sunday, 31 December. Its dominical letters hence are BA, such as the years 1916, 1944, 1972, 2000, and 2028 in the Gregorian calendar or, likewise, 2012 and 2040 in the obsolete Julian calendar. In the Gregorian calendar all centennial leap years start on Saturday; the next such year will be 2400, see below for more.
Episodes in the series subsequently follow Sam's reaction to each leap (typically ending the cold open with him uttering "Oh, boy!" on discovering his situation), and then working with Al and Ziggy to figure out his new identity and who he needs to help to "set right what once went wrong" and trigger the next leap. An episode typically ends as a cliffhanger, showing the first few moments of Sam's next leap (along with him again uttering "Oh, boy!" on discovering his situation), which is repeated in the following episode's cold open. Though initially Sam's leaping is believed by Al and the others on the Quantum Leap team to be random, the characters come to believe in later seasons that someone or something is controlling Sam's leaping, and this is a central focus of the show's finale episode, "Mirror Image".