In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
The Prophet [peace and blessings of Allaah be upon him] informed us that indeed the sign of Laylat al-Qadr is that the sun rises on the following morning without rays. The noble companion Ubay Bin Ka’b [may Allaah be pleased with him] closely observed this for many years and saw the sun rising without rays in the morning after the 27th night, and he used to swear by Allaah that Laylatul Qadr is on the 27th night due to this sign. But what is correct is that it can definitely be other than the 27th night. It can definitely be the 27th night for a number of years, the 21st night in other years or on the 23rd, 25th or other than them (i.e. 29th night). [فللاحتياط والحزم الاجتهاد في الليالي كلها – Therefore, one should pay close attention, being observant, diligent, determined and striving in all the nights]. [paraphrased] https://binbaz.org.sa/fatwas/27442/%D8%B9%D9%84%D8%A7%D9%85%D8%A7%D8%AA-%D9%84%D9%8A%D9%84%D8%A9-%D8%A7%D9%84%D9%82%D8%AF%D8%B1