See recommended Sunnah fasting days for any month.
The white days are the 13th, 14th, and 15th of each Hijri month. Fasting on these days is a recommended Sunnah.
The Prophet ﷺ used to fast on Mondays and Thursdays. These days are recommended for voluntary fasting.
Fasting on the Day of Arafah (9 Dhul Hijjah) and the Day of Ashura (10 Muharram) carries great reward. Follow your local moon‑sighting for exact dates.