Bada Mangal, or Budhwa Mangal, refers to a series of 4-5 Tuesdays that occur in the month of Jyeshtha according to the Hindu calendar, which is generally between May and June according to the Gregorian calendar. These 5 Tuesdays are considered to be extremely powerful, and devotion done during this time amplifies your positive energy.
And as Tuesdays are dedicated to Lord Hanuman, in the Budhwa Mangals devotees pray to Lord Hanuman for protection, strength, loyalty, and devotion.