When a specific month is designated as the time frame for divorce (e.g., Ramadan), precisely when does the divorce take effect?

Primary text

When one states, 'You are divorced in a specified month, such as Ramadan,' the divorce takes effect at the first instant of the first night of that month. This occurs upon sunset of the last day of the preceding month, which is Sha'ban. This is the position of Abu Hanifa. The reasoning is that the month was made a container (Dharf) for the divorce, so when the container's time begins, the divorce occurs, analogous to saying, 'If you enter the house, you are divorced,' which takes effect upon the first entry.