It is a recommended Sunnah (tradition) to fast on the 15th of Sha'ban. However, Islamic jurisprudence dictates that one should not fast exclusively on the 15th, but rather in conjunction with the 13th and 14th (the "White Days" or Ayyam al-Beed ) or by fasting the majority of Sha'ban, as was the practice of the Prophet Muhammad.
Remove one's name from the list of the wretched or deprived if it has been written there. nisf shaban