The Navarātrī (nine nights) festival is celebrated several times a year. The most important of which is Śārada Navarātri that comes in the fall season in the Northern Hemisphere, usually around October of each year. The Chaitra navarātri comes at the start of the summer season in the Indian subcontinent.
Navarātri or 9 Nights of Goddess are considered very important for Śaktas (who worship Divine Mother in the form of Śakti), in order to receive blessings of the Divine Mother Śakti in various forms such as Śrī Durga, Śrī Vārāhi, Śrī Lalita Tripurasundari, Śrī Śakambari, Śrī Cāmuṇḍā etc. Some worship the 9 forms of Durga, also called as Nava Durga on each day of the Navarātri-s.
The very beginning of Chaitra Navarātri, marks the start of the New Year for the Southern Indian states of Andhra, Telangana and Karnataka and is celebrated as the Ugādi festival. The eight day of the Navarātri, marks the birthday of Śrī Tārā Devi and the ninth day is celebrated as Śrī Rāma Navami, the birthday of Lord Rāma, who is revered as an incarnate of the Preserver of the Universe Lord Viṣṇu.
Prayers to the Daśamahāvidyā-s, the ten manifestations of the Divine Mother Kāli, recital of Śrī Lalita Sahasranāma, Śrī Durgā Saptaśati during these nine nights and days, is considered very auspicious and result fetching.
The festival falls on April 5th in the Western Hemisphere and April 6th in the Eastern Hemisphere and ends on April 12th and 13th respectively.