High Latitude Rules

High Latitude Rules

At high latitudes, summer nights can be very short, making it difficult to determine Fajr and Isha times. Al-Falak provides three rules for these situations.

HighLatitudeRule options

Rule	Behavior
MIDDLE_OF_THE_NIGHT	Fajr never earlier than middle of night, Isha never later (default)
SEVENTH_OF_THE_NIGHT	Fajr never earlier than start of last seventh, Isha never later than end of first seventh
TWILIGHT_ANGLE	Uses fajr_angle/60 and isha_angle/60 as night fractions

Using a high latitude rule

from alfalak import PrayerTimes, CalculationParameters, HighLatitudeRule

params = CalculationParameters(
    high_latitude_rule=HighLatitudeRule.MIDDLE_OF_THE_NIGHT,
)
prayer_times = PrayerTimes(
    (51.5074, -0.1278),  # London
    datetime.now(),
    calculation_parameters=params,
)

MIDDLE_OF_THE_NIGHT (default)

The night is split in half. Fajr cannot be earlier than the midpoint between sunset and sunrise, and Isha cannot be later than that midpoint.

SEVENTH_OF_THE_NIGHT

The night is split into sevenths. Fajr cannot be earlier than the start of the last seventh, and Isha cannot be later than the end of the first seventh.

TWILIGHT_ANGLE

Similar to seventh-of-the-night, but uses the Fajr and Isha angles divided by 60 as the night fraction. For example, with a Fajr angle of 18°, the fraction is 18/60 = 0.3 (30% of the night).

When to use these rules

These rules are most relevant for locations above ~48° latitude during summer months:

Latitude	Example locations
48°–55°	Paris, Berlin, Kyiv, London
55°–60°	Copenhagen, Oslo, Stockholm, St. Petersburg
60°+	Helsinki, Reykjavik, Anchorage, Longyearbyen

See also

• Polar Regions — handling polar day/night
• Calculation Methods — method-specific defaults