The state government's official 'Shiv Jayanti' celebrations are held on February 19 each year while the Shiv Sena celebrates it as per the "tithi".
"We demand that the government should celebrate the event as per the tithi," Sena activist Arvind Bhosle said, after a Shiv Jayanti celebration in Worli.
Blood donation camps were held to mark the occasion, he said.
State Industry Minister Subhash Desai, who is Mumbai's Guardian Minister, said his party (Sena) wants the government to celebrate the event as per the "tithi" which falls today this year.
"We pointed out that a committee appointed by the previous government had suggested that the Shiv Jayanti be celebrated as per the tithi - on Falgun Vadya Tritiya," the minister said.