Mohini Ekadashi occurs during the Shukla Paksha (waxing phase of moon) in the month of April/May. Ekadasi fasting, which falls on the 11th day of a lunar fortnight, is dedicated to Lord Vishnu. It is believed that one will be able to overcome sadness and remorse by observing Mohini Ekadasi. In 2009, the date of Mohini Ekadasi is May 5.
Mohini Ekadashi falls in the month of Vaishakha in calendars followed in North India and other regions. It falls during Chithirai Month in Tamil Calendar.
Importance of Mohini Ekadashi is mentioned in the Surya Purana. The greatness of it was narrated to Yudhishtira by Lord Krishna.

It is said that Lord Vashishta advised Lord Ram to observe Mohini Ekadashi to get over the remorse and distress caused from the separation from Mata Sita.

All the regular practices associated with Ekadasi are followed during Mohini Ekadasi. Those observing partial fast avoid rice.

Ekadashi is mentioned in a number of Puranas. It is associated with Lord Vishnu and ‘Haribhakti Vilas’ talks in detail about its importance. Today, in Hindu religion Ekadasi has come to mean a day to fast. It falls on the 11th day of every lunar fortnight and thus there are two Ekadashi in a month. It is also known as ‘Harivasara’ and ‘Hari din.’ Several Puranas including Padma Purana and Skanda Purana detail about the significance of Ekadeshi.

How to fast on Ekadashi?

How to observe ‘Ekadashi’ is clearly mentioned in ‘Harivasara.’ In modern day, many people will find it difficult to observe it in its entire strictness. But there are a large number of people who observe it. And there are numerous observations on what food one can have? There are also regional variations to the way in which the Ekadasi is observed.

The preparation starts on Dasami day – a day before Ekadashi. The person observing Ekadashi should wake up early in the morning on Dasami day and should take bath and perform other daily routines. The person should mentally prepare for the Ekadashi. He/She should only have one meal on the Dasami day and should avoid salt. Alcohol, non-vegetarian food and sex should be avoided. Some Puranas say ‘dal’ and ‘honey’ should be avoided on Dasami day.

The next day, that is the Ekadashi day, is meant for total fasting. Praying to Vishnu is the order of the day. Some people avoid sleep during Ekadashi night and they hear religious discourses and perform ‘Arati.’ But many people today will not be able to stay awake the entire night due to work pressure etc.

The next day on Dwadasi – that is the day after Ekadeshi – the same routine done on Dasami is followed. Overeating should be avoided on Dwadasi day. Puranas state that one should not take pride in observing Ekadashi. The food on Dwadasi should be cooked in one’s house.

It is good to go on fast once in a while as it recuperates the body. Ekadashi observance cleans our body and the digestive organs get much needed rest.

Those people suffering from ailments and on medications should take the advice of a doctor before fasting. Never torture your body in the name of religion. There is nothing wrong in having fruits or milk. And you can bring a certain amount of flexibility in the way it is observed.