If it is confirmed that Laylat al-Qadr is the 27th night, does it begin on the evening of the 26th until dawn, or on the evening of the 27th until dawn? And what is the evidence for that?

Scholars have differed regarding the exact night of Laylat al-Qadr. The most preponderant opinion is that it shifts among the last ten nights of Ramadan, being more emphasized on the odd-numbered nights, and the most likely among them is the 27th night. Sheikh Al-Uthaymeen held the view that it rotates among the odd-numbered nights in different years. The 27th night is the night preceding the 27th day, as the night is attributed to the day that follows it. This is what Al-Qasimi indicated, citing Allah's saying: ﴿It is not for the sun to overtake the moon, nor does the night outstrip the day. And each, in an orbit, is swimming.﴾ (Ya-Sin: 40).