“As-Sufuri said (may Allah have mercy on him):“I saw it written with my father’s hand from Shaykh Abul-Hasan Ash-Shadhili (Allah have mercy on him):

“Since I reached puberty I never missed seeing Laylatul-Qadr.
If the first day of Ramadan is a Sunday, it falls on the 29th;
if it is a Monday, it falls on the 21st;
if it is a Tuesday, it falls on the 27th;
if it is a Wednesday, it falls on the 29th like Sunday;
if it is a Thursday, it falls on the 25th;
if it is a Friday, it falls on the 27th like Tuesday;
if it is a Saturday, it falls on the 23rd, and Allah knows best.”

(Nuzhat Al-Majalis Wa Munkhatab An-Nafa’is” by Al-’Allama Ash-Shaykh ‘Abdur Rahman As-Sufuri Ash-Shafi