Himachal Pradesh and Gujarat will pick new assemblies on Nov 4 and Dec 13 and 17, respectively, in elections that will see a virtual straight fight between the ruling BJP and Congress in both states.
Chief Election Commissioner V.S. Sampath told the media here that votes in both states will be counted Dec 20.
These will be the most important state elections since Uttar Pradesh, India's most populous state, voted in February-March this year, along with Goa, Punjab, Uttarakhand and Manipur.
Both Himachal Pradesh (182 seats) and Gujarat (68 seats) are ruled by the Bharatiya Janata Party, with the Congress desperate to dislodge it.
The announcement came hours after Congress president Sonia Gandhi unleashed the Congress campaign in Gujarat with a stinging attack on the BJP.
"We are making foolproof security arrangements in both states by deploying adequate strength of central police forces," he said.
Armed police forces from other states would also be deployed in the two states.
Sampath said there would be strict monitoring of expenditure incurred by political parties and candidates as well as "paid news".
He said all candidates would be required to open separate bank accounts and incur expenditure only from these accounts.
The Election Commission, Sampath said, expects "the highest standards" of conduct and neutrality in election work from officials.
"Their work will be under constant watch and scrutiny." He added that the model code of conduct for political parties would be strictly enforced.
Sampath said the polling dates had been determined after taking into account climatic conditions, particularly in Himachal, academic calendar, festivals, law and order, and availability of security forces.