Vaishakh Amavasya is the No Moon day in Vaishakha month of Hindu calendar. It falls in May-June. In 2017, Vaishakh Amavasya date is May 25 in Marathi, Gujarati, Telugu & Kannada calendars. It is on April 26 as per North Indian Hindi calendars.
In Amavasyant Hindu calendars of Maharashtra, Gujarat, Telangana, Andhra Pradesh & Karnataka, Vaishakha Amavasya is observed as Shani Jayanti.
Vaishakh Amavasya in Amavasyant Hindu calendars = Jyeshta Amavasya in North Indian (Purnimant) Hindu calendars.
Vaishakh Amavasya is observed as Shani Jayanti according to Amavasyant calendars.