One of the few accounts that gives specific dates is that of the revival of Pontrhydfendigaid in J.J. Morgan’s biography of Dafydd Morgan. Here is the account relating the opening of the new chapel building on January 8, 1819:
Ebenezer Richard, Tregaron, D. Evans, Morfa-mawr, and William Davies, the founder of the cause, ministered. Such power attended the ministry that a fatal blow was dealt to the annual feast as an occasion of prodigality, games of chance, and drunkenness. In 1820 a School Association was held at Cwmystwyth on Easter Monday, and by it the second feast of Gehenna was driven away to oblivion in the area. The new place of worship was formed as a Sabbath circuit with Cwmystwyth. The Lord accepted the simple temple that was raised as home to his ark; he visited his people with a local revival, [Footnote: ‘Clearly a drop from the Beddgelert cloud.’] the house was filled with the cloud, namely the house of the Lord. The Lord gave to them quadruple for their sacrifice, and fifteen new members were added to the twelve disciples there already.
J.J. Morgan, Dafydd Morgan, pp. 3-4.
With thanks to Geraint Jones.