How we calculate
Dinam works everything out from astronomy. No figures are copied from another almanac.
Positions of the Sun and the Moon
Positions come from the open-source Astronomy Engine library (MIT licence), which follows the standard models used by observatories.
Places
Town and village locations and time zones come from GeoNames, used under the Creative Commons Attribution 4.0 licence. Towns with their own pages were checked by hand.
Sunrise and sunset
Sunrise and sunset are the moments the upper edge of the Sun touches the horizon, allowing for the usual bending of light by the air. This is the convention of Indian almanacs. The place used is the centre of the town you choose.
Ayanamsa
Nakshatra, yoga and the other star-based values use the sidereal zodiac with the Lahiri ayanamsa, the standard of the Indian national almanac. Dinam computes it from the position of the star Chitra (Spica), and it agrees with the published Lahiri value to a fraction of an arc-second.
The five parts
- Tithi: every 12° that the Moon moves ahead of the Sun. 30 tithis make a lunar month.
- Nakshatra: the Moon's sidereal position in 27 equal parts of 13°20′.
- Yoga: the Sun's and Moon's sidereal positions added together, in 27 equal parts.
- Karana: half of a tithi.
- Day: the almanac day runs from sunrise to the next sunrise. The names shown for a day are those in force at sunrise, with the time each one ends.
Daytime periods
The daytime from sunrise to sunset is divided into eight equal parts. Rahu kalam, Yamagandam and Gulika kalam are fixed parts that depend on the weekday:
| Weekday | Rahu | Yama | Gulika |
|---|---|---|---|
| Sunday | 8 | 5 | 7 |
| Monday | 2 | 4 | 6 |
| Tuesday | 7 | 3 | 5 |
| Wednesday | 5 | 2 | 4 |
| Thursday | 6 | 1 | 3 |
| Friday | 4 | 7 | 2 |
| Saturday | 3 | 6 | 1 |
Abhijit muhurtham is the 8th of 15 equal parts of the daytime, centred on local noon. It is shown but not marked as good on Wednesdays.
Accuracy
We check our results against widely used almanacs; they agree to within about a minute. A difference of a minute or two can come from rounding, height above sea level, or the exact point chosen in your town. Some families and regions follow different rules, especially for festival dates. For an important ceremony, please also ask your family astrologer or priest.