Ṛgveda Upākarma 2155: London, England

Ṛgveda Upākarma is the annual renewal of the sacred thread (yajñopavīta) observed by Ṛgveda-following households, traditionally anchored to Śravaṇa Nakṣatra in Śrāvaṇa Śukla Pakṣa.

Per the Kālatattva-Vivecana's compilation verses, the primary timing is Śravaṇa Nakṣatra; if that is unavailable or afflicted by Grahaṇa, Saṅkrānti, or Guru/Śukra Asta, Pañcamī Tithi is taken next, then Hasta Nakṣatra, and if none of those work in Śrāvaṇa māsa, the same order is tried again in Bhādrapada Śukla Pakṣa.

The table below shows the computed date, both for those repeating the observance and for those performing it for the first time.