Gregorian calendar in the context of "December solstice"

The Constitution of the Year XII (French: Constitution de l’an XII), also called the Organic Sénatus-consulte of 28 Floréal, year XII (Sénatus-consulte organique du 28 floréal an XII), was a national constitution of the First French Republic adopted during the Year XII of the French Revolutionary Calendar (1804 in the Gregorian calendar).

It amended the earlier Constitution of the Year VIII and Constitution of the Year X, establishing the First French Empire with Napoleon Bonaparte — previously First Consul for Life, with wide-ranging powers — as Napoleon I, Emperor of the French. The Constitution established the House of Bonaparte as France's imperial dynasty, making the throne hereditary in Napoleon's family. The Constitution of the Year XII was later itself extensively amended by the Additional Act and definitively abolished with the final return of the Bourbons in 1815.

Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian or Julian calendar, and are exactly equivalent to the Anno Domini (AD) and Before Christ (BC) notations. The expressions "2025 CE" and "AD 2025" each equally describe the current year; "400 BCE" and "400 BC" are the same year too. BCE/CE are primarily used to avoid religious connotations, by not referring to Jesus as Dominus [Lord].

A mnemonic device (/nəˈmɒnɪk/ nə-MON-ik), memory trick or memory device is any learning technique that aids information retention or retrieval in the human memory, often by associating the information with something that is easier to remember.

It makes use of elaborative encoding, retrieval cues and imagery as specific tools to encode information in a way that allows for efficient storage and retrieval. It aids original information in becoming associated with something more accessible or meaningful—which in turn provides better retention of the information.

A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A date is the designation of a single and specific day within such a system. A calendar is also a physical record (often paper) of such a system. A calendar can also mean a list of planned events, such as a court calendar, or a partly or fully chronological list of documents, such as a calendar of wills.

The Hijri calendar (Arabic: ٱلتَّقْوِيم ٱلْهِجْرِيّ, romanized: al-taqwīm al-hijrī), also known in English as the Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the annual fasting and the annual season for the great pilgrimage. In almost all countries where the predominant religion is Islam, the civil calendar is the Gregorian calendar, with Syriac month-names used in the Levant and Mesopotamia (Iraq, Syria, Jordan, Lebanon and Palestine), but the religious calendar is the Hijri one.

This calendar enumerates the Hijri era, whose epoch was established as the Islamic New Year in 622 CE. During that year, Muhammad and his followers migrated from Mecca to Medina and established the first Muslim community (ummah), an event commemorated as the Hijrah. In the West, dates in this era are usually denoted AH (Latin: Anno Hegirae, lit. 'In the year of the Hijrah'). In Muslim countries, it is also sometimes denoted as H from its Arabic form (سَنَة هِجْرِيَّة, abbreviated ھ). In English, years prior to the Hijra are denoted as BH ("Before the Hijra").

The terms anno Domini (AD) and before Christ (BC) are used when designating years in the Gregorian and Julian calendars. The term anno Domini is Medieval Latin and means "in the year of the Lord" but is often presented using "our Lord" instead of "the Lord", taken from the full original phrase "anno Domini nostri Jesu Christi", which translates to "in the year of our Lord Jesus Christ". The form "BC" is specific to English, and equivalent abbreviations are used in other languages: the Latin form, rarely used in English, is ante Christum natum (ACN) or ante Christum (AC).

This calendar era takes as its epoch the traditionally reckoned year of the conception or birth of Jesus. Years AD are counted forward since that epoch and years BC are counted backward from the epoch. There is no year zero in this scheme; thus the year AD 1 immediately follows the year 1 BC. This dating system was devised in 525 by the Eastern Roman monk Dionysius Exiguus but was not widely used until the 9th century. Modern scholars believe that the actual date of birth of Jesus was about 5 BC.

The French Republican calendar (French: calendrier républicain français), also commonly called the French Revolutionary calendar (calendrier révolutionnaire français), 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, meant to replace the Gregorian calendar. The calendar consisted of twelve 30-day months, each divided into three 10-day cycles similar to weeks, plus five or six intercalary days at the end to fill out the balance of a solar year. It was designed in part to remove all religious and royalist influences from the calendar, and it was part of a larger attempt at dechristianisation and decimalisation in France (which also included decimal time of day, decimalisation of currency, and metrication). It was used in government records in France and other areas under French rule, including Belgium, Luxembourg, and parts of the Netherlands, Germany, Switzerland, Malta, and Italy.

The Constitution of the Year X (French: Constitution de l'an X) was a national constitution of France adopted during the Year X (10) on 16 Thermidor (4 August) of the French Revolutionary Calendar (1802 in the Gregorian calendar). It amended the Constitution of the Year VIII, revising the Consulate to augment Napoleon Bonaparte's authority by making him First Consul for Life.

Both the Constitution of the Year X and the Constitution of the Year VIII were further amended by the Constitution of the Year XII, which established the First French Empire with Napoleon as Emperor.