It is known that Buddhists presented various theories about the duration of the True Teaching (saddharma). This article introduces a work explaining that the period of existence of the True Teaching is 5000 years, namely the Bhagavatyāmnāyānusāriṇī nāma vyākhyā written in the 12th century, a commentary on the Aṣṭasāhasrikā Prajñāpāramitā. It is known that the work follows the traditional interpretation of the Buddhist scriptures described in the Śatasāhasrikā Prajñāpāramitā Bṛhaṭṭīkā and the Āryaśatasāhasrikā-pañcaviṃśatisāhasrikāṣṭādaśasāhasrikā Prajñāpāramitā Bṛhaṭṭīkā. Thus, in this article, to examine and elucidate the background of the view that the True Teaching lasts 5000 years, I focus on the descriptions in the three above-mentioned works, translate the corresponding portions, and consider how those works influenced each other. As a result, I find it most likely that the explanation that the duration of True Teaching is 5000 years in the Bhagavatyāmnāyānusāriṇī nāma vyākhyā is based on the theory presented in the Śatasāhasrikā Prajñāpāramitā Bṛhaṭṭīkā and Āryaśatasāhasrikā-pañcaviṃśatisāhasrikāṣṭādaśasāhasrikā Prajñāpāramitā Bṛhaṭṭīkā.
