Julian calendar in the context of Polemius Silvius

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].

The Greek Orthodox Patriarchate of Jerusalem, also known as the Greek Orthodox Church of Jerusalem, is an autocephalous church within the wider communion of Eastern Orthodox Christianity. Established in the mid-fifth century as one of the oldest patriarchates in Christendom, it is headquartered in the Church of the Holy Sepulchre in Jerusalem and led by the patriarch of Jerusalem, currently Theophilos III. The patriarchate's ecclesiastical jurisdiction includes roughly 200,000 to 500,000 Orthodox Christians across the Holy Land in Palestine, Jordan and Israel.

The church traces its foundation in Jerusalem to the day of Pentecost, when the Holy Spirit, according to Christian beliefs, descended on the disciples of Jesus Christ and ushered the spread of the Gospel. The church celebrates its liturgy in the ancient Byzantine Rite – whose sacred language, Koine Greek, is the original language of the New Testament – and follows its own liturgical year under the Julian calendar.

The Pereiaslav Agreement or Pereyaslav Agreement (Ukrainian: Переяславська рада, romanized: Pereiaslavska Rada, lit. 'Pereiaslav Council', Russian: Переяславская рада) was an official meeting that convened for a ceremonial pledge of allegiance by Zaporozhian Cossacks to Russian tsar Alexis (r. 1645–1676) in the town of Pereiaslav in central Ukraine, in January 1654. The ceremony took place concurrently with ongoing negotiations that started on the initiative of Hetman Bohdan Khmelnytsky to address the issue of the Cossack Hetmanate with the ongoing Khmelnytsky Uprising against the Polish–Lithuanian Commonwealth and which concluded the Treaty of Pereiaslav (also known as the March Articles). The treaty itself was finalized in Moscow in April 1654 (in March according to the Julian calendar).

Khmelnytsky secured the military protection of the Tsardom of Russia in exchange for allegiance to the tsar. An oath of allegiance to the Russian monarch from the leadership of the Cossack Hetmanate was taken, shortly thereafter followed by other officials, the clergy and the inhabitants of the Hetmanate swearing allegiance. The exact nature of the relationship stipulated by the agreement between the Hetmanate and Russia is a matter of scholarly controversy. The council of Pereiaslav was followed by an exchange of official documents: the March Articles (from the Cossack Hetmanate) and the tsar's declaration (from Russia).

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 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 slightly differently to make the average calendar year 365.2425 days long rather than the Julian calendar's 365.25 days, thus more closely approximating the 365.2422-day "tropical" or "solar" year that is determined by the Earth's revolution around the Sun.

The rule for leap years is that every year divisible by four is a leap year, except for years that are divisible by 100, except in turn for years also divisible by 400. For example, 1800 and 1900 were not leap years, but 1600 and 2000 were leap years.

The Babylonian calendar was a lunisolar calendar used in Mesopotamia from around the 2nd millennium BC until the Seleucid Era (294 BC), and it was specifically used in Babylon from the Old Babylonian Period (1780s BC) until the Seleucid Era.

In the Seleucid Era it was reformed as "Greek time", Anno Graecorum was introduced and used in the Middle East and Egypt until the middle of the first millennium when the First Council of Nicaea AD 325 defined the Church year based on the Roman early Julian calendar. As Anno Graecorum formed the basis for time references in the Bible and spread westward, it rather increased the Babylonian calendars importance. The Babylonian calendar is also partly reflected in calendars in South and East Asia and the Islamic calendar as well as Iranian calendars. The Julian calendar inherited the definitions of the 12 month system, week, hour etc. from the Babylonian calendar and the current Jewish calendar can be seen as a slightly modified Babylonian calendar that still exists today and is practised, but with Anno Mundi Livryat haOlam year calculation since the creation of the world. Today's global time system UTC (Gregorian calendar) therefore has its main structure inherited from the Babylonian calendar.

The 7th century is the period from 601 through 700 in accordance with the Julian calendar in the Christian Era.

The spread of Islam and the Muslim conquests began with the unification of Arabia by the Islamic prophet Muhammad starting in 622. After Muhammad's death in 632, Islam expanded beyond the Arabian Peninsula under the Rashidun Caliphate (632–661) and the Umayyad Caliphate (661–750). The Muslim conquest of Persia in the 7th century led to the downfall of the Sasanian Empire. Also conquered during the 7th century were Syria, Palestine, Armenia, Egypt, and North Africa.

The 6th century is the period from 501 through 600 in line with the Julian calendar.

In the West, the century marks the end of Classical Antiquity and the beginning of the Middle Ages. The collapse of the Western Roman Empire late in the previous century left Europe fractured into many small Germanic kingdoms competing fiercely for land and wealth. From the upheaval the Franks rose to prominence and carved out a sizeable domain covering much of modern France and Germany. Meanwhile, the surviving Eastern Roman Empire began to expand under Emperor Justinian, who recaptured North Africa from the Vandals and attempted fully to recover Italy as well, in the hope of reinstating Roman control over the lands once ruled by the Western Roman Empire.

Eastern Lutheranism (also known as Byzantine Lutheranism or Byzantine Rite Lutheranism) refers to Eastern Protestant Lutheran churches, such as those of Ukraine and Slovenia, that use a form of the Byzantine Rite as their liturgy. It is unique in that it is based on the Eastern Christian rite used by the Eastern Orthodox Church, while incorporating theology from the Divine Service contained in the Formula Missae, the base texts for Lutheran liturgics in the West.

Eastern Lutherans use the Julian calendar for the calendar and thus observe feast days and liturgical seasons, such as Great Lent, in a fashion similar to Orthodox customs. As such, many Byzantine Lutheran holy days are shared with those of the Eastern Orthodox Church; in addition, Eastern Lutheran churches are constructed in accordance with Byzantine architecture. Posture during worship, such as bowing, is identical to that in other parts of Eastern Christianity. Within Byzantine Rite Lutheranism, the calendar of saints includes persons esteemed in Eastern Christianity, such as John Chrysostom and Nestor the Chronicler, as well as those specific to the Lutheran Church, such as Lucas Cranach the Elder and Martin Luther.

The Dormition of the Mother of God is a Great Feast of the Eastern Orthodox, Oriental Orthodox, and Eastern Catholic Churches (except the East Syriac churches). It celebrates the "falling asleep" (death) of Mary the Theotokos ("Mother of God", literally translated as God-bearer), and her being taken up into heaven. The Feast of the Dormition is observed on August 15, which for the churches using the Julian calendar corresponds to August 28 on the Gregorian calendar. The Armenian Apostolic Church celebrates the Dormition not on a fixed date, but on the Sunday nearest 15 August. In Western Churches the corresponding feast is known as the Assumption of Mary, with the exception of the Scottish Episcopal Church, which has traditionally celebrated the Falling Asleep of the Blessed Virgin Mary on August 15.

Christian canonical scriptures do not record the death or Dormition of Mary. Hippolytus of Thebes, a 7th- or 8th-century author, writes in his partially preserved chronology of the New Testament that Mary lived for 11 years after the death of Jesus, dying in AD 41.

March is the third month of the year in both the Julian and Gregorian calendars. Its length is 31 days. In the Northern Hemisphere, the meteorological beginning of spring occurs on the first day of March. The March equinox on the 20 or 21 marks the astronomical beginning of spring in the Northern Hemisphere and the beginning of autumn in the Southern Hemisphere, where September is the seasonal equivalent of the Northern Hemisphere's March.

The knuckle mnemonic is a mnemonic device for remembering the number of days in the months of the Julian and Gregorian calendars.

The Fasti (Latin: Fāstī [ˈfaːstiː], "the Calendar"), sometimes translated as The Book of Days or On the Roman Calendar, is a six-book Latin poem written by the Roman poet Ovid and made public in AD 8. Ovid is believed to have left the Fasti incomplete when he was exiled to Tomis by the emperor Augustus in 8 AD. Written in elegiac couplets and drawing on conventions of Greek and Latin didactic poetry, the Fasti is structured as a series of eye-witness reports and interviews by the first-person vates ("poet-prophet" or "bard") with Roman deities, who explain the origins of Roman holidays and associated customs—often with multiple aetiologies. The poem is a significant, and in some cases unique, source of fact in studies of religion in ancient Rome; and the influential anthropologist and ritualist J.G. Frazer translated and annotated the work for the Loeb Classical Library series. Each book covers one month, January through June, of the Roman calendar, and was written several years after Julius Caesar replaced the old system of Roman time-keeping with what would come to be known as the Julian calendar.

The popularity and reputation of the Fasti has fluctuated more than that of any of Ovid's other works. The poem was widely read in the 15th–18th centuries, and influenced a number of mythological paintings in the tradition of Western art. However, as scholar Carole E. Newlands has observed, throughout the 20th century "anthropologists and students of Roman religion … found it full of errors, an inadequate and unreliable source for Roman cultic practice and belief. Literary critics have generally regarded the Fasti as an artistic failure." In the late 1980s, however, the poem enjoyed a revival of scholarly interest and a subsequent reappraisal; it is now regarded as one of Ovid's major works, and has been published in several new English translations. Ovid was exiled from Rome for his subversive treatment of Augustus, yet the Fasti continues this treatment—which has led to the emergence of an argument in academia for treating the Fasti as a politically weighted work.

The 2nd century is the period from AD 101 (represented by the Roman numerals CI) through AD 200 (CC) in accordance with the Julian calendar. It is considered part of the Classical era, epoch, or historical period.

Early in the century, the Roman Empire attained its greatest expansion under the emperor Trajan, but after his death became primarily defensive for the rest of its history. Much prosperity took place throughout the empire at this time, ruled as it was by the "Five Good Emperors", a succession of well-received and able rulers. This period also saw the removal of the Jews from Jerusalem during the reign of Hadrian after Bar Kokhba's revolt.