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108 lines
4.6 KiB
Markdown
108 lines
4.6 KiB
Markdown
# pray_calc_dart
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[](https://pub.dev/packages/pray_calc_dart)
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[](https://github.com/acamarata/pray-calc-dart/actions/workflows/ci.yml)
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[](LICENSE)
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Islamic prayer times for Dart and Flutter. Pure Dart port of [pray-calc](https://github.com/acamarata/pray-calc), implementing the NREL Solar Position Algorithm, MCW seasonal model, and dynamic twilight angles. Zero dependencies.
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## Installation
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```yaml
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dependencies:
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pray_calc_dart: ^1.0.0
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```
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## Quick Start
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```dart
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import 'package:pray_calc_dart/pray_calc_dart.dart';
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void main() {
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final date = DateTime(2024, 3, 15);
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final times = getTimes(date, 40.7128, -74.0060, -5.0);
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print('Fajr: ${formatTime(times.fajr)}');
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print('Sunrise: ${formatTime(times.sunrise)}');
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print('Dhuhr: ${formatTime(times.dhuhr)}');
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print('Asr: ${formatTime(times.asr)}');
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print('Maghrib: ${formatTime(times.maghrib)}');
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print('Isha: ${formatTime(times.isha)}');
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print('Qiyam: ${formatTime(times.qiyam)}');
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}
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```
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## API
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### `getTimes(date, lat, lng, tz, {elevation, temperature, pressure, hanafi})`
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Computes all prayer times for a given date and location.
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| Parameter | Type | Default | Description |
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| --- | --- | --- | --- |
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| `date` | `DateTime` | required | Local date (time-of-day ignored) |
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| `lat` | `double` | required | Latitude (-90 to 90, south negative) |
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| `lng` | `double` | required | Longitude (-180 to 180, west negative) |
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| `tz` | `double` | required | UTC offset in hours (e.g., -5 for EST) |
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| `elevation` | `double` | 0 | Observer elevation in meters |
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| `temperature` | `double` | 15 | Ambient temperature in Celsius |
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| `pressure` | `double` | 1013.25 | Atmospheric pressure in mbar |
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| `hanafi` | `bool` | false | Hanafi Asr (2x shadow) vs Shafi'i (1x) |
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Returns a `PrayerTimes` object with fractional-hour values for: `qiyam`, `fajr`, `sunrise`, `noon`, `dhuhr`, `asr`, `maghrib`, `isha`, and the computed `angles`.
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### `getAngles(date, lat, lng, {elevation, temperature, pressure})`
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Computes dynamic twilight depression angles using the three-layer model:
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1. MCW seasonal base (piecewise-linear, latitude-dependent)
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2. Ephemeris corrections (Earth-Sun distance, Fourier season smoothing)
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3. Environmental corrections (elevation dip, atmospheric refraction)
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Returns `TwilightAngles` with `fajrAngle` and `ishaAngle` in degrees, clipped to [10, 22].
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### `getSpa(date, lat, lng, tz, {...})`
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Full NREL Solar Position Algorithm. Accurate to +/-0.0003 degrees for zenith angle. Supports custom zenith angles for twilight calculations.
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### `formatTime(hours)`
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Converts fractional hours to an `HH:MM:SS` string. Returns `"N/A"` for non-finite values.
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### Additional Functions
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- `solarEphemeris(jd)` -- Jean Meeus Ch. 25 low-precision ephemeris
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- `toJulianDate(date)` -- DateTime to Julian Date
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- `getAsr(solarNoon, latitude, declination, {hanafi})` -- Asr computation
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- `getQiyam(fajrTime, ishaTime)` -- Last third of the night
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- `getMscFajr(date, latitude)` -- MCW Fajr offset in minutes
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- `getMscIsha(date, latitude, [shafaq])` -- MCW Isha offset in minutes
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- `minutesToDepression(minutes, latDeg, declDeg)` -- Time to angle conversion
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## Dynamic Angle Algorithm
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Fixed-angle methods (ISNA 15 degrees, MWL 18 degrees, etc.) produce inaccurate Fajr times at latitudes above 45 degrees N/S. The dynamic method adapts the depression angle based on season, latitude, Earth-Sun distance, and local atmospheric conditions.
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Result: approximately 18 degrees at the equator, approximately 12-14 degrees at 50-55 degrees N in summer. Matches observational data from the Moonsighting Committee Worldwide.
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## Compatibility
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Dart SDK 3.7.0+. Works in Flutter (iOS, Android, Web, Desktop), Dart CLI, and server-side Dart. Zero external dependencies.
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## Related
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- [pray-calc](https://github.com/acamarata/pray-calc) - TypeScript/JavaScript version (npm)
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- [nrel-spa](https://github.com/acamarata/nrel-spa) - Standalone NREL SPA for JavaScript
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- [qibla](https://github.com/acamarata/qibla) - Qibla direction calculator
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## Acknowledgments
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The Solar Position Algorithm is based on:
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> Reda, I. and Andreas, A. (2004). Solar Position Algorithm for Solar Radiation Applications. NREL/TP-560-34302. [DOI: 10.2172/15003974](https://doi.org/10.2172/15003974)
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The MCW seasonal model is based on the work of the [Moonsighting Committee Worldwide](http://moonsighting.com/isha_fajr.html) (Khalid Shaukat).
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## License
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[MIT](LICENSE). The NREL SPA implementation carries its own terms (see LICENSE for details).
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