How to Find a Blue Moon Using Panchang JSON

DevDarsha API — Wed, 03 Jun 2026 10:03:15 +0000

How to Find a Blue Moon Using Panchang JSON

A Blue Moon is often misunderstood.

It does not usually mean that the Moon turns blue in color. In common modern calendar usage, a Blue Moon means the second Full Moon in the same Gregorian calendar month.

This is a useful example where modern calendar logic and Indian Panchang data can be compared.

In the Panchang system, the Full Moon is represented by Purnima Tithi. So if we can detect two Purnima dates inside one Gregorian month, we can identify the second one as the Blue Moon reference.

For this example, we will use Kolkata, India and the month of May 2026.

Live reference:

https://platform.devdarsha.com/playground

What We Are Checking

The rule is simple:

If one Gregorian month has two Full Moon / Purnima dates,
the second one is called a Blue Moon.

So for May 2026, we need to check whether there are two Purnima dates.

## First Purnima: 1 May 2026

From DevDarsha Panchang JSON for Kolkata:

{
  "date": "2026-05-01",
  "weekday": "Friday",
  "timezone": "Asia/Kolkata",
  "city": "Kolkata",
  "tags": [
    "shukla_paksha",
    "purnima"
  ],
  "tithi": [
    {
      "number": 15,
      "name": "Purnima",
      "paksha": "Shukla",
      "start": "01-05-2026 05:04:20",
      "end": "01-05-2026 22:54:20"
    }
  ]
}

This confirms that 1 May 2026 is a Purnima date for Kolkata.

## Second Purnima: 31 May 2026

Now check another date in the same Gregorian month:

{
  "date": "2026-05-31",
  "weekday": "Sunday",
  "timezone": "Asia/Kolkata",
  "city": "Kolkata",
  "tags": [
    "shukla_paksha",
    "purnima"
  ],
  "tithi": [
    {
      "number": 15,
      "name": "Purnima",
      "paksha": "Shukla",
      "start": "31-05-2026 04:51:47",
      "end": "31-05-2026 14:16:09"
    },
    {
      "number": 16,
      "name": "Pratipada",
      "paksha": "Krishna",
      "start": "31-05-2026 14:16:09",
      "end": "01-06-2026 16:38:39"
    }
  ]
}

This confirms that 31 May 2026 is also a Purnima date for Kolkata.

Result

May 2026 has two Purnima dates for Kolkata:

Date	Panchang Result	Calendar Meaning
1 May 2026	Purnima	First Full Moon of May 2026
31 May 2026	Purnima	Second Full Moon of May 2026

Therefore:

31 May 2026 = Blue Moon reference for Kolkata

How a User Can Find a Blue Moon

A user can follow this method:

Select a city.
Check each date in a Gregorian month.
Look for Panchang JSON where tithi.name is Purnima.
Count how many Purnima dates occur in that same month.
If there are two, the second Purnima is the Blue Moon.

In JSON terms, look for either:

"tags": ["shukla_paksha", "purnima"]

or:

"tithi": [
  {
    "name": "Purnima",
    "paksha": "Shukla"
  }
]

## Simple JavaScript Logic

Here is a basic example of how this can be detected programmatically:

const monthData = [
  {
    date: "2026-05-01",
    city: "Kolkata",
    tags: ["shukla_paksha", "purnima"],
    tithi: [{ name: "Purnima", paksha: "Shukla" }]
  },
  {
    date: "2026-05-31",
    city: "Kolkata",
    tags: ["shukla_paksha", "purnima"],
    tithi: [
      { name: "Purnima", paksha: "Shukla" },
      { name: "Pratipada", paksha: "Krishna" }
    ]
  }
];

const purnimaDates = monthData.filter(day =>
  day.tags.includes("purnima") ||
  day.tithi.some(t => t.name === "Purnima")
);

if (purnimaDates.length >= 2) {
  const blueMoonDate = purnimaDates[1].date;
  console.log(`Blue Moon reference date: ${blueMoonDate}`);
}

Output:

Blue Moon reference date: 2026-05-31

Panchang vs Blue Moon

The important point is that Blue Moon is not originally a Panchang term.

It is based on the Gregorian calendar.

Concept	Panchang System	Blue Moon Concept
Basis	Tithi	Gregorian calendar month
Full Moon term	Purnima	Full Moon
Cycle	Lunar	Calendar-month comparison
Detection	Shukla Paksha Purnima	Second Full Moon in same month
Example	1 May and 31 May 2026 are Purnima	31 May 2026 is the Blue Moon

So the Panchang helps identify the Full Moon dates, while the Gregorian calendar decides whether the second one is called a Blue Moon.

Why City and Timezone Matter

Lunar events should be checked city-wise because Panchang calculations depend on location and timezone.

For this example, the data is for:

City: Kolkata
Timezone: Asia/Kolkata

A different city or timezone may shift the local calendar date for certain lunar events, especially when the Tithi starts or ends near sunrise or midnight.

Live JSON Reference

You can verify this using DevDarsha Playground:

https://platform.devdarsha.com/playground

Use these two dates for Kolkata:

2026-05-01
2026-05-31

Both dates return Purnima in the Panchang data.

References

DevDarsha Playground
https://platform.devdarsha.com/playground

NASA Moon Phases
https://science.nasa.gov/moon/moon-phases/

Timeanddate Blue Moon Explanation
https://www.timeanddate.com/astronomy/moon/blue-moon.html

Timeanddate Kolkata Moon Phases
https://www.timeanddate.com/moon/phases/india/kolkata

How to Get Hindu Calendar and Panchang Data as JSON

DevDarsha API — Wed, 03 Jun 2026 09:56:17 +0000

When building Indian calendar apps, astrology tools, festival pages, or regional date features, one common problem appears very quickly: normal Gregorian dates are not enough.

A Hindu calendar page usually needs more than day, month, and year. It may need Tithi, Nakshatra, Yoga, Karana, Vara, Paksha, sunrise, sunset, moon phase, and festival logic. These values can also change by location, because sunrise time and local calendar rules matter.

That is why using structured Panchang data through JSON is easier than manually maintaining static festival tables.

What data is usually needed?

A useful Panchang API response should include:

Tithi
Nakshatra
Yoga
Karana
Vara
Paksha
Sunrise and sunset
Moon data
Festival information
Location-based calculation

For example, a calendar app may need to answer a simple question:

What is the Hindu calendar date for this city on this Gregorian date?

But internally, that answer depends on astronomical calculations and traditional Panchang rules.

Why JSON helps developers

JSON makes the data easy to use in websites, mobile apps, dashboards, and backend services.

A frontend app can call an API and show the result directly. A backend system can store the response, compare dates, or generate monthly calendar views.

Example use cases:

Hindu calendar websites
Festival reminder apps
Panchang widgets
Astrology dashboards
Regional calendar tools
Date conversion features
Educational calendar pages

Testing Panchang data live

I am building DevDarsha API for this exact use case. It provides Panchang and Hindu calendar data through structured JSON endpoints.

You can test a live Panchang response here:

https://platform.devdarsha.com/playground

The documentation is available here:

https://platform.devdarsha.com/documentation

Basic integration idea

A simple integration usually follows this flow:

Select a Gregorian date.
Select a city or location.
Send the request to the Panchang API.
Read the JSON response.
Display Tithi, Nakshatra, sunrise, sunset, and festival data in the app.

This keeps the application clean because the calendar logic stays inside the API layer instead of being hardcoded inside the frontend.

Final note

For small personal projects, static Hindu calendar data may be enough. But for apps that need city-based results, festival accuracy, or future date calculations, an API-based approach is easier to maintain.

DEV Community: DevDarsha API

How to Find a Blue Moon Using Panchang JSON

How to Get Hindu Calendar and Panchang Data as JSON