The Gregorian calendar is the calendar used in most of the world. It is named after Pope Gregory XIII, who introduced it in October 1582; the calendar spaces leap years to make the average year 365.2425 days long, approximating the 365.2422-day tropical year, determined by the Earth's revolution around the Sun. The rule for leap years is: Every year, divisible by four is a leap year, except for years that are divisible by 100, but these centurial years are leap years if they are divisible by 400. For example, the years 1700, 1800, 1900 are not leap years, but the years 1600 and 2000 are; the calendar was developed as a correction to the Julian calendar, shortening the average year by 0.0075 days to stop the drift of the calendar with respect to the equinoxes. To deal with the 10 days' difference that this drift had reached, the date was advanced so that 4 October 1582 was followed by 15 October 1582. There was no discontinuity of the Anno Domini calendar era; the reform altered the lunar cycle used by the Church to calculate the date for Easter, restoring it to the time of the year as celebrated by the early Church.

The reform was adopted by the Catholic countries of Europe and their overseas possessions. Over the next three centuries, the Protestant and Eastern Orthodox countries 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 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 specified by the year, the month, the day of the month. Although the calendar year runs from 1 January to 31 December, at previous times year numbers were based on a different starting point within the calendar.

In the Julian calendar, a leap year occurred every 4 years, the leap day was inserted by doubling 24 February. The Gregorian reform left the leap day unchanged. However, it has become customary in the modern period to number the days sequentially with no gaps, 29 February is 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. Calendar cycles repeat every 400 years, which equals 146,097 days. Of these 400 years, 303 are regular years of 365 days and 97 are leap years of 366 days. A mean calendar year is 365+97/400 days = 365.2425 days, or 365 days, 5 hours, 49 minutes and 12 seconds. The Gregorian calendar was a reform of the Julian calendar, it was instituted by papal bull Inter gravissimas dated 24 February 1582 by Pope Gregory XIII, after whom the calendar is named. The motivation for the adjustment was to bring the date for the celebration of Easter to the time of year in which it was celebrated when it was introduced by the early Church.

The error in the Julian calendar had led to the date of the equinox according to the calendar drifting from the observed reality, thus an error had been introduced into the calculation of the date of Easter. Although a recommendation of the First Council of Nicaea in 325 specified that all Christians should celebrate Easter on the same day, it took five centuries before all Christians achieved that objective by adopting the rules of the Church of Alexandria; because the date of Easter is a function – the computus – of the date of the spring equinox, the Catholic Church considered unacceptable the increasing divergence between the canonical date of the equinox and observed reality. Easter is celebrated on the Sunday after the ecclesiastical full moon on or after 21 March, adopted as approximation to the March equinox. European scholars had been well aware of the calendar drift since the early medieval period. Bede, writing in the 8th century, showed that the accumulated error in his time was more than three days.

Roger Bacon in c. 1200 estimated the error at eight days. Dante, writing c. 1300, was aware of the need of a calendar reform. The first attempt to go forward with such a reform was undertaken by Pope Sixtus IV, who in 1475 invited Regiomontanus to the Vatican for this purpose. However, the project was interrupted by the death of Regiomontanus shortly after his arrival in Rome; the increase of astronomical knowledge and the precision of observations towards the end of the 15th century made the question more pressing. Numerous publications over the following decades called for a calendar reform, among them two papers sent to the Vatican by the University of Salamanca in 1515 and 1578, but the project was not taken up again until the 1540s, implemented only under Pope Gregory XIII. In 1545, the Council of Trent authorized Pope Paul III to reform the calendar

William S. Kaufman was an American architect known for designing a number of public buildings in Indiana and Ohio. Kaufman was born in Union County, Indiana to Elias and Mary Kaufman, who were Pennsylvania natives and early Indiana settlers, he attended school in Brownsville and trained as a carpenter and stair-builder in Cambridge City, Indiana. He studied architectural drafting in Indianapolis and remained there until 1876, when he moved to New Castle and opened an office moving his practice to Richmond, Indiana, his son, joined him in the architecture business for a time and moved to Indianapolis and to California with his wife, the noted Ragtime composer May Aufderheide Kaufman. A daughter, Maude Kaufman Eggemeyer became an accomplished artist of the Richmond Group of painters. Westmoreland County Courthouse, Pennsylvania The Westcott Hotel, Indiana Richmond State Hospital, Indiana (superintendent of construction for architect E. H. Ketcham Lindley Hall at Earlham College Parry Hall at Earlham College Fayette County, Indiana Courthouse, Indiana renovation Wayne County Courthouse (superintendent of construction for architect James McLaughlin Winchester, Indiana Friends Meeting House Wysor Street Depot, Indiana Greenville Carnegie Library, Ohio Central Christian Church, Indiana Henry Henley Public Library, Indiana Tomlan, Mary Raddant and Michael A. Richmond, Indiana: Its Physical and Aesthetic Heritage to 1920, Indianapolis: Indiana Historical Society, 2003 Kieser, David L. "Carthage Historic District Study", Indianapolis: Kieser Consulting Group, LLC, 2015 William S. Kaufman at Find a Grave

The Snake Decides is an album by British jazz saxophonist Evan Parker. It was released in 1988 on Parker and Derek Bailey's Incus Records label, re-released on Parker's Psi label in 2003, it is out of print. The album features four unaccompanied saxophone solos, recorded by sound engineer Michael Gerzon in St Paul's Church, England in 1986; the Penguin Guide to Jazz awarded the album one of its rare crown accolades, in addition to featuring it as part of its Core Collection. It declares the album to be a great recording as a record, "an essential document of modern music"; the wood cut reproduced on the cover is by George Murphy. All compositions by Evan Parker"The Snake Decides" – 19:56 "Leipzig Folly" – 11:42 "Buriden's Ass" – 6:29 "Haine's Last Tape" – 6:01 Evan Parker – soprano saxophone