The Manmohan Singh-led coalition government will be sworn in at 1730 hours on Saturday, a Rashtrapati Bhavan spokesman said late Friday night.
President A P J Abdul Kalam will administer the oath of office and secrecy to Dr Manmohan Singh at the Ashoka Hall in Rashtrapati Bhavan.
Rashtrapati Bhavan has received a communique about the ceremony from the prime minister-designate's office.
It is not immediately clear how many ministers will be sworn in along with Dr Singh, but sources said the team is likely to be small to begin with.
Earlier, Congress spokesman Tom Vadakkan told rediff.com late on Friday night, "As of now, the swearing-in will take place between 4 pm and 5 pm on Saturday."
"But so much is happening that we don't know about," he added.
Uncertainty about the ceremony had prevailed through Friday evening and into the night amid intense jockeying over ministerial berths inside the Congress and from its allies.
Reportage: PTI/Onkar Singh in New Delhi