Devaśayanī Ekādaśī · Āṣāḍhī Ekādaśī
Devaśayanī Ekādaśī
Devaśayanī Ekādaśī is associated with Viṣṇu and the beginning of his symbolic period of repose in many traditions. Ekādaśī means the eleventh tithi in either half of the lunar month. In Maharashtra, Āṣāḍhī Ekādaśī has a particularly strong association with Viṭṭhala of Paṇḍharpur and the devotional Vārkarī pilgrimage tradition. Many Vaiṣṇava calendars also treat this day as the beginning of Cāturmāsya, the traditional four-month observance period; other traditions may define its beginning or commitments differently.

Why it appears
Devaśayanī Ekādaśī appears when Śukla Ekādaśī prevails at sunrise in regular amānta Āṣāḍha.
Śukla Ekādaśī must be present at local sunrise, and the amānta calendar used here must give the regular month Āṣāḍha. When both are true, Open Pañcāṅga shows Devaśayanī Ekādaśī instead of repeating the general Ekādaśī observance.
Devotees may fast, pray, sing kīrtana, worship Viṣṇu or Viṭṭhala, undertake pilgrimage, or follow other practices according to their tradition. A complete Smārta or Vaiṣṇava calendar may also apply aruṇodaya, Mahādvādaśī, and pāraṇa rules.
Context reference: Maharashtra Tourism, Āṣāḍhī Ekādaśī