What is the expiation for delaying the making up of days from one Ramadan until the next for several years due to a shortage of days in Sha'ban?

It is advisable to hasten to make up for the missed Ramadan fasts to clear one's conscience and obey Allah. As for a woman who missed making up a day of fasting before the next Ramadan because she thought Sha'ban was thirty days, but it turned out to be less, she is not required to offer expiation (kaffarah) for that day, nor is she considered negligent, due to her inability to make up that day in Sha'ban.