Electricity Forward Agreement (calendar) (short: EFA system) is a calendar used to specify load profiles when trading on the electricity market. It was officially only valid until October 2014 but is still abundantly used among commodity traders. [1] [2]
One distinguishes between weekdays WD and weekend WE since the electricity consumption is clearly lower on Saturdays and Sundays. An EFA day starts at 11pm local time and runs through 11pm the next (astronomical) day. An EFA-week WK consists of five WD and two WE-days. An EFA month is defined differently than common months: March, June, September, and December have five weeks, while all other months are considered to have exactly four weeks. The two EFA seasons are winter (WK 40 – WK 13) and summer (WK 14 – WK 39), each having exactly 26 weeks. Due to the existence of leap years, some EFA-Decembers have six weeks (e.g. 2004 and 2009), a strong difference from the commonly used Gregorian calendar system, where February is the leap month. [3]
The EFA day is composed of six blocks of 4 hours each. For each block, baseload products exist (i.e. WD 1/2/3/4/5/6 and WE 1/2/3/4/5/6). Peak load products only exist for WD3, WD4, and WD5 (also on bank holidays), and consequently off-peak products are only available for the remaining EFA blocks of each week. Blocks 1 and 2 are usually termed overnight blocks; the other blocks are day blocks. [4]
Generally speaking, a calendar year begins on the New Year's Day of the given calendar system and ends on the day before the following New Year's Day, and thus consists of a whole number of days. A year can also be measured by starting on any other named day of the calendar, and ending on the day before this named day in the following year. This may be termed a "year's time", but not a "calendar year". To reconcile the calendar year with the astronomical cycle certain years contain extra days. The Gregorian year, which is in use in most of the world, begins on January 1 and ends on December 31. It has a length of 365 days in an ordinary year, with 8760 hours, 525,600 minutes, or 31,536,000 seconds; but 366 days in a leap year, with 8784 hours, 527,040 minutes, or 31,622,400 seconds. With 97 leap years every 400 years, the year has an average length of 365.2425 days. Other formula-based calendars can have lengths which are further out of step with the solar cycle: for example, the Julian calendar has an average length of 365.25 days, and the Hebrew calendar has an average length of 365.2468 days. The Lunar Hijri calendar is a lunar calendar consisting of 12 months in a year of 354 or 355 days. The astronomer's mean tropical year, which is averaged over equinoxes and solstices, is currently 365.24219 days, slightly shorter than the average length of the year in most calendars.
The French Republican calendar, also commonly called the French Revolutionary calendar, was a calendar created and implemented during the French Revolution, and used by the French government for about 12 years from late 1793 to 1805, and for 18 days by the Paris Commune in 1871, and meant to replace the Gregorian calendar.
The Hebrew calendar, also called the Jewish calendar, is a lunisolar calendar used today for Jewish religious observance and as an official calendar of Israel. It determines the dates of Jewish holidays and other rituals, such as yahrzeits and the schedule of public Torah readings. In Israel, it is used for religious purposes, provides a time frame for agriculture, and is an official calendar for civil holidays alongside the Gregorian calendar.
Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of days or months.
A leap year is a calendar year that contains an additional day compared to a common year. The 366th day is added to keep the calendar year synchronised with the astronomical year or seasonal year. Since astronomical events and seasons do not repeat in a whole number of days, calendars having a constant number of days each year will unavoidably drift over time with respect to the event that the year is supposed to track, such as seasons. By inserting ("intercalating") an additional day—a leap day—or month—a leap month—into some years, the drift between a civilization's dating system and the physical properties of the Solar System can be corrected.
The International Fixed Calendar (also known as the Cotsworth plan, the Cotsworth calendar, the Eastman plan or the Yearal was a proposed calendar reform designed by Moses B. Cotsworth, first presented in 1902. The International Fixed Calendar divides the year into 13 months of 28-days each. A type of perennial calendar, every date is fixed to the same weekday every year. Though it was never officially adopted at the country level, the entrepreneur George Eastman instituted its use at the Eastman Kodak Company in 1928, where it was used until 1989. While it is sometimes described as the 13-month calendar or the equal-month calendar, various alternative calendar designs share these features.
A common year starting on Friday is any non-leap year that begins on Friday, 1 January, and ends on Friday, 31 December. Its dominical letter hence is C. The most recent year of such kind was 2021 and the next one will be 2027 in the Gregorian calendar, or, likewise, 2022 and 2033 in the obsolete Julian calendar, see below for more. This common year is one of the three possible common years in which a century year can begin on, and occurs in century years that yield a remainder of 100 when divided by 400. The most recent such year was 1700 and the next one will be 2100.
Dominical letters or Sunday letters are a method used to determine the day of the week for particular dates. When using this method, each year is assigned a letter depending on which day of the week the year starts. The Dominical letter for the current year 2024 is GF.
A leap year starting on Monday is any year with 366 days that begins on Monday, 1 January, and ends on Tuesday, 31 December. Its dominical letters hence are GF. The current year, 2024, is a leap year starting on Monday in the Gregorian calendar. The last such year was 1996 and the next such year will be 2052 in the Gregorian calendar or, likewise, 2008 and 2036 in the obsolete Julian calendar.
Calendar reform or calendrical reform is any significant revision of a calendar system. The term sometimes is used instead for a proposal to switch to a different calendar design.
A leap year starting on Wednesday is any year with 366 days that begins on Wednesday 1 January and ends on Thursday 31 December. Its dominical letters hence are ED. The most recent year of such kind was 2020 and the next one will be 2048 in the Gregorian calendar, or likewise, 2004 and 2032 in the obsolete Julian calendar, see below for more.
The positivist calendar was a calendar reform proposal by Auguste Comte (1798–1857) in 1849. Revising the earlier work of Marco Mastrofini, or an even earlier proposal by "Hirossa Ap-Iccim", Comte developed a solar calendar with 13 months of 28 days, and an additional festival day commemorating the dead, totalling 365 days.
The determination of the day of the week for any date may be performed with a variety of algorithms. In addition, perpetual calendars require no calculation by the user, and are essentially lookup tables. A typical application is to calculate the day of the week on which someone was born or a specific event occurred.
A leap week calendar is a calendar system with a whole number of weeks in a year, and with every year starting on the same weekday. Most leap week calendars are proposed reforms to the civil calendar, in order to achieve a perennial calendar. Some, however, such as the ISO week date calendar, are simply conveniences for specific purposes.
A perpetual calendar is a calendar valid for many years, usually designed to look up the day of the week for a given date in the past or future.
The Indian national calendar, called the Shaka calendar or Śaka calendar, is a solar calendar that is used alongside the Gregorian calendar by The Gazette of India, in news broadcasts by All India Radio, and in calendars and official communications issued by the Government of India. Śaka Samvat is generally 78 years behind the Gregorian calendar, except from January to March, when it is behind by 79 years.
The ISO week date system is effectively a leap week calendar system that is part of the ISO 8601 date and time standard issued by the International Organization for Standardization (ISO) since 1988 and, before that, it was defined in ISO (R) 2015 since 1971. It is used (mainly) in government and business for fiscal years, as well as in timekeeping. This was previously known as "Industrial date coding". The system specifies a week year atop the Gregorian calendar by defining a notation for ordinal weeks of the year.
The Dreamspell is an esoteric calendar in part inspired by the Maya calendar by New Age spiritualist, Mayanist philosopher, and author José Argüelles and Lloydine Burris Argüelles. The Dreamspell calendar was initiated in 1987 and released as a board game in 1990.
The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull Inter gravissimas issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years differently so as to make the average calendar year 365.2425 days long, more closely approximating the 365.2422-day 'tropical' or 'solar' year that is determined by the Earth's revolution around the Sun.
The Hanke–Henry Permanent Calendar (HHPC) is a proposal for calendar reform. It is one of many examples of leap week calendars, calendars that maintain synchronization with the solar year by intercalating entire weeks rather than single days. It is a modification of a previous proposal, Common-Civil-Calendar-and-Time (CCC&T). With the Hanke–Henry Permanent Calendar, every calendar date always falls on the same day of the week. A major feature of the calendar system is the abolition of time zones.
