Jatismara Vrata is an auspicious vratha which is observed by devotees who want to remember his past life memories. A Jatismara means the one who remembers his / her past life incidents.
Various Gods like Lord Ganesha, Surya Bhagavan, Lord Vishnu, Lord Shiva are worshipped simultaneously. Mauna Vrata (observance of silence) is observed till moon rises. The major merit or benefit of this vrata is – his memory power will increase and even he can recollect the events of his past lives.
There is no in-depth explanation on the procedure or vidhi of Jatismara Vrata is mentioned in Puranas. But the reference about Jatismara Vrata is there in the Bhavishya Purana.