New Delhi, June 6 -- As the battle for market share between India's top two stock exchanges hots up, the capital markets regulator has directed both to furnish modalities on a proposed shift in their weekly index options settlement dates by 15 June before it approves any changes, two people aware of the matter said.

"The Securities and Exchange Board of India (Sebi) has instructed the bourses to apprise it about when they would issue a circular to their broking members on potential expiry day shift to ensure markets have enough time to adapt to the change," the first person said.

He explained that besides weekly index derivatives contracts, exchanges like BSE and NSE run three monthly contracts concurrently-for eg. June, July and August...