How we calculate
Every date and time on this site comes from one calculation engine. An AI model never sets a date or a time. The engine runs once for each city when the site is built.
The short version
- The day runs from sunrise to sunrise. The tithi of the day is the tithi in force at sunrise.
- The moments that decide a date come from NASA JPL’s DE440 ephemeris, worked out ahead of time and stored in tables.
- Sunrise, sunset and moonrise are worked out for the exact city.
- Each date shows its city, its rule, the times that decide it and the sources of the rule, so you can check it against your own pandit.
- When a date could go either way, the page says so (“close call”) and shows the other date.
What the engine uses
| Engine | @sd/panchang 0.1.0 |
|---|---|
| Ephemeris | NASA JPL DE440 (transition tables 2020 to 2035). It gives the instant a tithi, nakshatra, yoga, karana or sankranti begins. |
| Ayanamsa | Lahiri, IAE 1985 value (23°15′00.658″ on 21 March 1956) |
| Dates we can show | 2020 to 2035. The engine refuses a date outside that range. It never guesses. |
| Time zones | IANA zone names. Daylight saving is handled. A time on another civil day is marked “+1 day” or “−1 day”. |
The settings we use for every city
These are the engine’s defaults. We do not change them for any city, except the month system.
| Sunrise | Upper limb of the Sun with standard refraction (Drik Panchang’s default and the US Naval Observatory’s). Some almanacs use the centre of the disc with no refraction (“Hindu rising”). That is 3 to 6 minutes later in India and more at high latitude. We do not use it. A boundary that falls within 5 minutes of the deciding moment is marked as a close call. |
|---|---|
| Moonrise | Centre of the Moon’s disc at the geometric horizon, no refraction. This matches Drik Panchang to the minute for Karva Chauth. The US Naval Observatory definition (upper limb, with refraction) is 4 to 6 minutes earlier. The later time is also the safer one for a fast that ends at moonrise. |
| Month system | Purnimanta (the month ends at the full moon), except for cities in states that use amanta (the month ends at the new moon). Amanta cities: Mumbai, Kolkata, Chennai, Bengaluru, Hyderabad, Ahmedabad, Surat, Pune, Thiruvananthapuram. Purnimanta cities in India: New Delhi, Jaipur, Lucknow, Varanasi, Patna, Chandigarh, Bhopal. Cities abroad use purnimanta. The two systems name the dark fortnight differently. The day of a festival is the same in both. Pages show both month names. |
| Tradition | Smarta. For Ekadashi, Janmashtami and Gita Jayanti we show the Vaishnava date beside it, on the same screen. |
| Second date in India | Where the date in New Delhi differs from the date in your city, the page shows it as “In India (New Delhi)”. |
| High latitude | If the Sun does not rise or set, the engine uses the times at latitude 65° and labels the day. No city on this site is that far north. |
The day, and the tithi
A tithi is the time the Moon takes to gain 12 degrees on the Sun. It begins and ends at one instant for the whole world. It lasts about 19 to 26 hours. The panchang assigns it to the civil day by local sunrise.
If a tithi ends before the next sunrise, it can touch no sunrise at all. It is then “lost” (kshaya). If it spans two sunrises, it “repeats” (vriddhi). That is why a festival such as Navratri can run for eight to ten civil days.
Festival dates
Each festival is a rule held as data: the month, the fortnight, the tithi (or nakshatra, or the Sun’s entry into a sign), the window of the day that decides it, and a tie-break. Every festival page shows the rule in words and the sources the engine cites for it, and a line that says what decides the date (for example “Amavasya ends 6:16 PM; sunset 5:36 PM”). Where one rule needs special care (Lakshmi Puja in the evening, Janmashtami at midnight, Holika Dahan and Raksha Bandhan outside Bhadra, Karva Chauth at moonrise), the page says so.
The same festival can fall on different days in different cities, because the tithi is fixed and the local sunrise, sunset or moonrise is not. We never show India’s date as everyone’s date.
Traditions, months and years
We never call another tradition’s date wrong. Only an arithmetic error is wrong. Your temple may follow its own calendar, and then its date comes first for you. Years are named by their era: Vikram Samvat and Shaka Samvat. An extra (adhika) month is marked. Annual festivals never fall in an adhika month; monthly vrats do. Adhika months in the years we cover: Ashwin 2020, Shravana 2023, Jyeshtha 2026, Chaitra 2029, Bhadrapada 2031 and Ashadha 2034. For Ugadi, Gudi Padwa and Chaitra Navratri in 2029, check the date with your tradition, because some begin the year in the adhika month.
Four rules we inferred
For four festivals we did not find the exact wording in a primary text. We inferred the rule from published reference dates, and it reproduces every one of them. We tell you here so you can judge it.
- Lakshmi Puja (Diwali). A day counts when Amavasya covers at least one ghatika (24 minutes) of the evening pradosh. If both days count, or neither, the second day. This reproduces all 154 cells of Drik Panchang’s 14-city table for 2022 to 2032.
- Janmashtami, Smarta. Ashtami must hold at midnight (nishita). If only the first day has it, but the next day has Ashtami at sunrise and the Rohini nakshatra joins it after that sunrise, the next day is kept. This reproduces all 112 cells of Drik Panchang’s Janmashtami table.
- Navratri. Navratri runs from Ghatasthapana to the parana day, the first daytime after Navami ends. This gives 11 to 20 October 2026, the span Drik Panchang and a New York temple both publish.
- Gita Jayanti. It is the Mokshada Ekadashi fast day. In Washington DC in 2026 that is 19 December, with the Vaishnava date, 20 December, shown beside it.
Known differences
These are the places where we differ from a reference, or where a rule has an open question. Nothing here is a failing test. The engine’s own file, KNOWN_DIFFERENCES.md, lists each one with its times.
What you may see
- A minute’s difference. Our tithi times come from NASA JPL and can show one minute later than Drik Panchang’s, because Drik’s tithi times run about 30 seconds earlier and are cut to the minute. Example: Amavasya 2024 ends 6:17 PM here and 6:16 PM there. We show the time as the engine gives it, cut to the minute the same way.
- Moonrise. See the setting above. We follow Drik Panchang’s convention.
Rules with an open question
- Smarta Ekadashi when Dvadashi is lost. When Dvadashi does not reach the next morning, householders fast on the day Ekadashi begins, even though Dashami holds the sunrise. The source is a summary of the Nirnayasindhu, Dharmasindhu and Kala-Madhava rules. This moves 31 of 396 New Delhi Ekadashis between 2020 and 2035 to the earlier day. It matches widely published dates. A Dvadashi that outlasts sunrise by under a minute is treated as ended; the page marks it a close call.
- Vaishnava Ekadashi. We follow the 2008 GCal algorithm: fixed arunodaya of 96 minutes, with its mahadvadashi and parana cases. A newer version of that program may differ in details. The Smarta and Vaishnava dates differ for 84 of the 396 New Delhi Ekadashis. For Janmashtami we take midnight as the middle of the night; GCal may use civil midnight.
- Holika Dahan. The rule “3½ prahars after sunrise” is read as seven eighths of the daytime. In New Delhi in 2026 the margin is under 20 minutes, so the definition matters and needs review. We do not yet compute Bhadra Mukha and Punchha. When Bhadra lasts past midnight and that clause does not apply, the engine gives the time after Bhadra ends and tells you to ask a priest.
- Single-source or default tie-breaks. Maha Shivaratri and Masik Shivaratri, Raksha Bandhan, Guru Purnima, Naraka Chaturdashi (Drik Panchang uses moonrise to sunrise), Govardhan Puja, Vijayadashami, Durga Puja in Bengal, Onam, Karthigai Deepam, Thaipusam, Varalakshmi Vratam, Pana Sankranti, Hanumath Jayanthi (Tamil), Rath Yatra, the Pitru Paksha shraddha days and the monthly vrats follow one source or a stated default. Each page shows the rule it used. Some almanacs choose differently.
Where references disagree with each other
- Makar Sankranti 2026 in New York. Drik Panchang says 14 January (the Sun enters Makara at 4:43 AM EST, before sunrise). A New York temple lists 13 January. We give 14 January and carry the note.
- Diwali 2024. Drik Panchang gives 1 November for New Delhi and 31 October for Mumbai. We reproduce both.
What we do not compute yet
- Lagna windows (the Diwali sthir lagna window, the Kanya lagna for Ghatasthapana). Drik Panchang adds these; we show the pradosh window and say so.
- Eclipses and sutak.
- The vakya panchangam used by many Tamil temples, and the Bengal clause for sankranti at night. Tamil temples may differ from us by a day.
- A skipped (kshaya) month. None occurs between 2020 and 2035.
- Any date before 2020 or after 2035.
What this cannot do
- Printed panchangs and temple calendars can differ from ours by a minute or two, or by a day on a close call.
- A temple may follow its own calendar. Its date then comes first for its members.
- Near the poles the Sun may not rise. The engine then uses the stated policy and labels the day.
How it is checked
The engine is checked against NASA JPL Horizons, against the US Naval Observatory for sunrise and sunset, and against published temple calendars and Drik Panchang’s dates, which we read by hand and do not copy. 131 automated tests pass as of 2026-10-12. Every date and time in our domain notes passes, within a 2 minute tolerance. Known differences are listed on this page.
The line on every date page
Calculated for your location from NASA JPL's DE440 ephemeris and Astronomy Engine (MIT licence), with the Lahiri ayanamsa. Times can differ by a minute or two from printed panchangs. For vrat and puja timings, follow your family or temple tradition.
If you find an error
Use “Report a problem” on any page, or the report form. Tell us your city and your tradition. A wrong fast date is fixed within 24 hours. Every fix is logged on the corrections page. If your temple keeps another day, read why dates can differ first.
Independence
Pujadeep is independent. It is not affiliated with Gita Press, ISKCON, the Bhaktivedanta Book Trust, any temple trust or Drik Panchang.