The Messenger of Allah (ﷺ) used to 𝐜𝐨𝐮𝐧𝐭 𝐭𝐡𝐞 𝐝𝐚𝐲𝐬 𝐢𝐧 𝐒𝐡𝐚'𝐛𝐚𝐧 in a manner he did not count any other month; then he fasted when he sighted the new moon of Ramadan; but if the weather was cloudy, he counted thirty days and then fasted.

Sunan Abu Dawood 2325