In Jain Dharma, the time of breaking a fast (parna) is always based on a practical “day” defined by local sunrise and sunset, not on the astronomical fact that daylight may last many months near the poles.

Because polar regions have very long days and nights, Jains living there normally do NOT treat one “sunrise to next sunset” (which could be months apart) as one upvās day. Instead, they follow a conventional 24‑hour day, using an agreed rule such as:

1. Use local clock time, not literal polar sunrise/sunset.

- Define a “Jain day” as 24 hours. - Fix a standard “sunrise time” (e.g., 6:00 am) and “sunset time” (e.g., 6:00 pm) by convention for purposes of dharma rules.

1. When to break a one‑day fast (upvās):

For a normal one‑day fast in such places, most reliable way is: - Start fast from one “sunset” (e.g., 6:00 pm) or after last meal of the previous day. - Break the fast after the next “sunrise time” (e.g., after 6:00 am next morning), ideally around Navkārsi time (≈48 minutes after that “sunrise”, say 6:48–7:00 am), within a short parna‑kāl window. ( jainknowledge.com)

1. Core principles that must be preserved:

- No eating or drinking at “night”. So even if it is physically bright outside for months, you follow the agreed “night hours” (for example, 6:00 pm–6:00 am) as if it were dark. ( jainknowledge.com) - Parna must be “after sunrise, never before”. Here, “sunrise” is the conventional start of the dharmic day, not literal sun‑disc rising. - All eating and (if allowed) boiled water should still be within “daytime hours” of that conventional schedule.

1. Why this is acceptable in Jain view:

- The essence of the rule is: - Fast for about one day in a regular, disciplined way. - Avoid night‑eating. - Keep parna within a short, pure, day‑time window. ( jainknowledge.com) - When the natural cycle is abnormal (like at the poles), acharya / guru guidance allows practical adjustment so the bhāva (inner intention) and basic structure of the vow stay intact.

1. What you should practically do if you live near the North Pole:

- Ask a knowledgeable Jain monk / nun or your local sangh how they define: - “Sunrise time” and “sunset time” for your city. - Exact parna window (e.g., between 6:48–7:30 am on the chosen day). ( jainknowledge.com) - Once that is fixed, always keep your one‑day fast from one defined “night” to the next defined “daybreak”, and break it only in that parna‑kāl.

In short: Even in places where the sun may not set for months, Jains do not wait 6 months to break a “day‑long” fast. They use a fixed 24‑hour schedule with agreed “day” and “night” times and break the fast after the next conventional “sunrise”, within the proper parna‑kāl.

You can read more on related fasting and parna rules here:

• How to break fast (Parna)
• Timing of breaking fast