There are many people who want to know which are the Hindu fasting dates. This is an easy to question to answer – you can fast 365 days. Yes in Hinduism all days are auspicious and you can fast on any day as you wish. All the seven days in a week are dedicated to a particular god – like Monday is dedicated to Lord Shiva and there are thousands of Hindus who regularly observe a fast on Mondays.
Apart from this weekly fasts there are fortnightly fast like on the eleventh day after full moon and no moon. This is the Ekadasi fasting and is dedicated to Lord Vishnu.
Another fortnightly fast is the Pradosh fasting – it is observed on the 13th day after full moon (Purnima) and no moon (Amavas) and is dedicated to Lord Shiva.
Then there is monthly fasting like Sankashti Chaturthi dedicated to Lord Ganesha – this is observed on the fourth day after full moon.
Another monthly fasting is dedicated to Lord Muruga – this is observed on the sixth day after no moon or Amavasi and is known as Sashti.
Then there are fasting which is observed for consecutive Fridays etc like the Solah Shukravar Vrat (sixteen Friday fasting) dedicated to Santoshi Mata. Another similar vrat is Solah Mangalvar Vrat (sixteen Monday fasting) dedicated to Lord Shiva.
Lord Hanuman devotees observe fast on Tuesdays.
Those who are under the influence of Shani or Saturn observe fast on Saturday.
Then there are numerous other fasting dates which fall once in a year like the Hartalika Teej Vrat, Vat Savitri Vrat etc.
You can read more about the weekly fasts in this article – Each day of week dedicated to a particular god in Hindu Pantheon.