The term "11 sep rahu kaal" functions as a noun phrase, as it names a specific astrological event. It refers to the precise time interval on September 11th that is considered inauspicious according to Vedic astrology. This period, known as Rahu Kaal or Rahu Kalam, is one of eight segments into which the daylight hours of a day are divided. It is believed to be under the malefic influence of Rahu, a celestial entity (lunar node) in this system.
The calculation of this specific period is dynamic and depends on the local sunrise and sunset times for the given date and geographical location. The total duration of daylight (from sunrise to sunset) is divided into eight equal parts, or muhurtas. A specific part is pre-assigned to Rahu Kaal for each day of the week in a fixed, non-sequential order: Monday (2nd part), Saturday (3rd), Friday (4th), Wednesday (5th), Thursday (6th), Tuesday (7th), and Sunday (8th). To determine the exact timing for September 11th of any given year, one must first identify the corresponding day of the week and then apply this formula to the local daylight hours.
Practically, adherents of Vedic astrology avoid initiating any significant or auspicious activities during Rahu Kaal. This includes actions such as starting a new business, signing contracts, making large purchases, beginning a journey, or conducting important ceremonies. The underlying belief is that undertakings commenced during this interval are prone to encountering obstacles, delays, or negative outcomes. Therefore, identifying the exact timing of Rahu Kaal for a specific date like September 11th is a crucial step for planning important events within this astrological framework.
