Fasting on the day where’s there doubt

 Question: What do we do no the day where there’s doubt whether it’s the first day of the month of Ramadan or the last day of Shaban?

Answer: Fasting on the day where there is doubt with the intention that its Ramadan is void, but if one makes the intention that if it’s the last day of Shaban then it’s a mustahab fast and if it’s it the first day of Ramadan, then it’s a wajib fast.