When does the divorce occur if the statement is 'You are divorced in the first daylight of the month of Ramadan,' or 'on the first day of it'?

Primary text

The divorce takes effect at the emergence of the dawn (Fajr) of the first day, as this is the beginning of both daylight (Nahar) and the day (Yawm). This is why a vow of seclusion (I'tikaf) or fasting for one day necessitates beginning from the break of dawn.