Işık Method

One minus the number of the year is multiplied by 4.367. The figure assigned to the month concerned is added to the integer of the number obtained.
When the total is divided by seven, the remainder shows the number of days from Friday.
The figures assigned to the twelve Arabic months are relatively the first letters of the twelve capitalized words in the following mnemonic couplet:
Hilmi, Be not Drifted by Hopeless Zeal of Earth!
Jilting Damsel Was to the Zealous its Beauty’s Joy.
The succession of the twelve capital letters in the couplet is the same as the succession of the twelve Arabic months beginning with Muharram.
As an example, let us find the twenty-ninth day of the month of Dhu’l-qa’da 1362: Let us multiply the number 1361 by 4.367; the answer is 5943. Now let us add two to this, –for the number assigned to Dhu’lqa’da is two–; the answer is 5945. If we divide this by seven the remainder is two. So, the first day of Dhu’l-qa’da is the second day beginning with Friday: It is Saturday. And the twenty-ninth day is again, naturally, Saturday. This method, discovered by Hüseyn Hilmi Işık ‘rahmatullâhi ta’âlâ ’alaih’.

Book : Seâdet-i Ebediyye Endless Bliss, Hakikat Kitabevi, Istanbul.