Indian national calendar in the context of "Ashwin"

Chaitra (Sanskrit: चैत्र, romanized: Caitra) is the first month of the Hindu lunar calendar and the Indian national calendar. The name of the month is derived from the position of the Moon near the Chitra nakshatra (star) on the full moon day. The month corresponds to spring (Vasanta) season and falls in March–April in the Gregorian calendar.

In the Hindu solar calendar, it corresponds to the last month of Mina and begins with the Sun's entry into Pisces. It corresponds to Choitro, the last month in the Bengali calendar, and Chait, the last month in the Nepali calendar (Vikram Samvat). In the Tamil calendar, it corresponds to the third month of Chittirai, falling in the Gregorian months of April–May.

The Hindu calendar, also called Panchanga (Sanskrit: पञ्चाङ्ग), is one of various lunisolar calendars that are traditionally used in the Indian subcontinent and Southeast Asia, with further regional variations for social and Hindu religious purposes. They adopt a similar underlying concept for timekeeping based on sidereal year for solar cycle and adjustment of lunar cycles in every three years, but differ in their relative emphasis to moon cycle or the sun cycle and the names of months and when they consider the New Year to start. Of the various regional calendars, the most studied and known Hindu calendars are the Shalivahana Shaka (associated with the King Shalivahana and basis for the Indian national calendar) found in the Deccan region of Southern India and the Vikram Samvat (Bikrami) found in Nepal and the North and Central regions of India – both of which emphasize the lunar cycle. Their new year starts in spring. In regions such as Tamil Nadu and Kerala, the solar cycle is emphasized and this is called the Tamil calendar (though Tamil Calendar uses month names like in Hindu Calendar) and Malayalam calendar and these have origins in the second half of the 1st millennium CE. A Hindu calendar is sometimes referred to as Panchangam (पञ्चाङ्गम्), which is also known as Panjika in Eastern India.

The ancient Hindu calendar conceptual design is also found in the Babylonian calendar, the Chinese calendar, and the Hebrew calendar, but different from the Gregorian calendar. Unlike the Gregorian calendar which adds additional days to the month to adjust for the mismatch between twelve lunar cycles (354 lunar days) and approximately 365 solar days, the Hindu calendar maintains the integrity of the lunar month, but inserts an extra full month, once every 32–33 months, to ensure that the festivals and crop-related rituals fall in the appropriate season.

The recorded pre-colonial history of the Philippines, sometimes also referred to as its "protohistoric period" begins with the creation of the Laguna Copperplate Inscription in 900 AD and ends with the beginning of Spanish colonization in 1565. The inscription on the Laguna Copperplate Inscription itself dates its creation to 822 Saka (900 AD). The creation of this document marks the end of the prehistory of the Philippines at 900 AD, and the formal beginning of its recorded history. During this historical time period, the Philippine archipelago was home to numerous kingdoms and sultanates and was a part of the Indosphere and Sinosphere.

Sources of precolonial history include archeological findings; records from contact with the Song dynasty, the Brunei Sultanate, Korea, Japan, and Muslim traders; the genealogical records of Muslim rulers; accounts written by Spanish chroniclers in the 16th and 17th centuries; and cultural patterns that at the time had not yet been replaced through European influence.

Phalguna or Phagun is the twelfth and last month of the Hindu lunar calendar and the Indian national calendar. The name of the month is derived from the position of the Moon near the Pushya nakshatra (star) on the full moon day. The month corresponds to the end of the winter (Shishira) season and falls in January–February of the Gregorian calendar.

In the Hindu solar calendar, it corresponds to the month of Kumbha and begins with the Sun's entry into Aquarius. It corresponds to Falgun, the eleventh month in the Bengali calendar and Vikram Samvat. In the Tamil calendar, it corresponds to the twelfth and last month of Panguni, falling in the Gregorian months of March–April. In the Vaishnav calendar, it corresponds to the twelfth month of Govinda.

In Ancient Indian astronomy, there are 27 nakshatras, or sectors along the ecliptic. A list of them is first found in the Vedanga Jyotisha, a text dated to the final centuries BCE. The nakshatra system predates the influence of Hellenistic astronomy on Vedic tradition, which became prevalent from about the 2nd century CE. There are various systems of enumerating the nakshatras; although there are 27–28 days to a sidereal month, by custom only 27 days are used. The following list gives the corresponding regions of sky. Months in the modern Indian national calendar, which is based on the traditional "nirayana" sidereal calendar, are named after twelve of the nakshatras, but do not coincide with the times when the sun is passing through these nakshatras - in fact, they are close to the opposite. It is possible that during the original naming of these months—whenever that happened—they were based on the position of the Full Moon (opposite the Sun). The modern Indian national calendar is a solar calendar, much like the Gregorian calendar, wherein solstices and equinoxes fall on the same date(s) every year.

Vaisakha (Sanskrit: वैशाख, IAST: Vaiśākha) is the second month of the Hindu lunar calendar and the Indian national calendar. The name of the month is derived from the position of the Moon near the Vishākhā nakshatra (star) on the full moon day. It corresponds to April–May in the Gregorian calendar. The month corresponds to the end of the spring (Vasanta) season and falls in April–May of the Gregorian calendar.

In the Hindu solar calendar, it corresponds to the month of Mesha and begins with the Sun's entry into Aries. It corresponds to Boishakh, the first month in the Bengali calendar. In the Tamil calendar, it corresponds to the third month of Vaikasi, falling in the Gregorian months of May–June. In the Vaishnav calendar, it corresponds to the third month of Madhusudanah.

Kārtika, Karttika or Kartik is the eighth month of the Hindu lunar calendar and the Indian national calendar. The name of the month is derived from the position of the Moon near the Kṛttikā nakshatra (star) on the full moon day. The month corresponds to the autumn season and falls in October–November of the Gregorian calendar.

In the Hindu solar calendar, it corresponds to the month of Tula and begins with the Sun's entry into Libra. It corresponds to Kartik, the seventh month in the Bengali calendar, and Kartika, the seventh month in Vikram Samvat. In the Tamil calendar, it corresponds to the eighth month of Karthigai, falling in the Gregorian months of November–December. In the Vaishnav calendar, it corresponds to the eighth month of Damodara.