The most effective time for meditation is brahma muhurta. Brahma muhurta starts 1 hour and 36 minutes before sunrise. It lasts for 48 minutes and thus ends 48 minutes before sunrise. There is no specific time for brahma muhurta as it differs per location and season. If meditation is not possible at this time; in the morning before breakfast, in the afternoon at dusk, in the evening before bed or at midnight are beneficial times as well.
To best time to meditate is determined due to the flow of ida and pingala nadi, the subtle energy channes, located in the psychic body. Ida nadi is connected to the left nostril and pingala to the right. Ida is the conductor of manas shakti, mental energy, and pingala is the conductor of prana shakti, vital energy. The major part of the day, one of the two nostrils is more open and its respective nadi will be predominant; either there is more mental or vital energy. When ida is dominant, it is time for mental work (mental energy), whereas when pingala is dominant, it is time for physical work (vital energy). At some particular times of the day, both ida and pingala, the left and the right nostril, are equally opened. Neither there is more mental, nor vital energy, and both nadis are in balance. This happens naturally during dusk and dawn. When ida and pingala are in balance; the sushumna nadi, the central nadi, opens. The sushumna is the conductor of spiritual energy. This is the channel through which kundalini rises once it is awakened. Thus, when ida and pingala nadi are balanced, the body and mind are prepared for meditation. To balance the nadis, one can perform at least three rounds of nadi sodhana pranayama before meditation.