kollavarsham 1.2.1

Malayalam calendar (Kollavarsham / Malayalam Era) for Dart. Convert between Gregorian and Malayalam dates, with month names, nakshatra, tithi and Malayalam numerals.

1.2.1

Fixed

• vishu is the day of the first sunrise after the Mesha sankranti, not always Medam 1: when the sankranti falls after sunrise but before the month-start cut-off (14 April 2026, 09:39), Vishu is the next day (15 April 2026, as in Kerala's holiday list). Checked against 2021–2026.

1.2.0

Added

• Yoga and Karana, with yogaAt, yogaOn, yogaSpanAt, karanaAt, karanaOn and karanaSpanAt.
• Kalam and KollavarshamCalendar.kalamOn: Rahu kalam, Gulika kalam and Yamagandam.
• KollavarshamCalendar.moonrise and moonset.
• KollavarshamCalendar.chandrashtamam, with Rashi.eighth, Rashi.fromSiderealLongitude and Nakshatra.rashiOf.
• Festivals: Sivaratri, Ashtami Rohini, Vinayaka Chathurthi, Durgashtami, Mahanavami, Vijayadasami, Deepavali, Guruvayur Ekadashi and Thaipooyam.
• Vrat and KollavarshamCalendar.vratDays: Ekadashi, Pradosham, Shashti, Pournami and Amavasya for a year.
• ChristianFeast, christianFeastsIn and easterSunday.
• HijriFestival, hijriFestivalsIn and tabularHijriToGregorian: tentative dates from the tabular Hijri calendar.

Fixed

• onam, attukalPongala, thrissurPooram and so festivalsIn threw for years in which the star fell between two sunrises, sunsets or midnights (for example Kollavarsham 1096).
• festivalsOn missed a festival listed under the next year, such as an Atham that falls in Karkidakam.

1.1.0

Added

• BirthDetails.fromInstant and BirthDetails.fromLocalTime: nakshatra with pada, rashi, tithi and Malayalam date of a moment of birth.
• Rashi, the twelve sidereal signs.
• Recurrence, with occurrencesBetween, next and JSON conversion: NakshatraInMonth (pirannal), NakshatraMonthly, TithiInMonth (shraddham), TithiEveryPaksha (every Ekadashi and the like), MalayalamDateYearly, MalayalamDateMonthly and GregorianYearly.
• DuplicateRule and AbsentRule, for days that are doubled or missing.

1.0.0

First stable release. The public API is now covered by semantic versioning.

• KollavarshamCalendar.verifiedMonthStarts is unmodifiable.
• Tests run on the web (Chrome) as well as the VM.

Changes since 0.1.0, in summary:

• Gregorian ↔ Kollavarsham conversion, cross-checked against the Swiss Ephemeris for every month 1900–2100 and backed by a precomputed table.
• Verified month starts for borderline months, with monthStartMargin.
• MalayalamDate formatting and parsing in Malayalam script and transliteration, with Malayalam digits.
• Nakshatra and tithi, with start and end times.
• Kerala festivals: Onam, Vishu, Attukal Pongala, Thrissur Pooram, Karkidaka Vavu, Mandala season and more.
• North Malabar year numbering (YearStart.kanni).

0.3.0

Breaking

• MalayalamDate.internal and KollavarshamCalendar.dayNumberOf, fromDayNumber, dateOfDayNumber and dayNumberOfGregorian are now @internal.
• MalayalamDate == compares calendars by value (location, year convention, overrides) instead of identity.

Added

• MalayalamDate.parse / tryParse, MalayalamMonth.tryParseName.
• Format tokens MMM, E, G and GGGG.
• YearStart.kanni for North Malabar year numbering.
• ObserverLocation and KollavarshamCalendar value equality.
• Festivals: Attukal Pongala, Thrissur Pooram, Karkidaka Vavu; KeralaFestival, festivalsIn(year) and festivalsOn(date).
• Every public member is documented.

0.2.0

• Solar theory cross-checked against the Swiss Ephemeris for every sankranti 1900–2100 (all within one minute).
• ΔT now comes from a yearly table (IERS observed values, then the Stephenson–Morrison–Hohenkerk 2016 extrapolation) for 1900–2100.
• Precomputed month-start table for ME 1075–1276: conversions for the default location take well under a microsecond. Disable with KollavarshamCalendar(usePrecomputedTable: false).
• Verified month start: Vrischikam 1197 began on 2021-11-16.
• Borderline-month audit (tool/borderline_audit.dart) and its list in test/fixtures/borderline_months.csv.
• Supported range is now explicit: KollavarshamCalendar.minYear (1) to maxYear (2000); dates outside throw a RangeError.
• Internal caches are bounded.

0.1.0-dev

• Gregorian ↔ Kollavarsham conversion using the Kerala sankranti rule (VSOP87 Sun, Lahiri ayanamsa, location-aware sunrise and sunset).
• MalayalamDate with arithmetic, comparison, formatting and a DateTime.toMalayalamDate() extension.
• Month, weekday, nakshatra and tithi names in Malayalam script and transliteration; Malayalam digit helpers.
• Nakshatra and tithi at sunrise or any instant, with start and end times.
• Festival dates: Onam, Atham, Vishu, Mandala season, Mandala Pooja and Makaravilakku.
• Verified month-start overrides and monthStartMargin for borderline months.