When did president of India refer to supreme court of India for advice?

As per Article 143 of Indian Constitution the President has a power to consult Supreme Court viz

(1) If at any time it appears to the President that a question of law or fact has arisen, or is likely to arise, which is of such a nature and of such public importance that it is expedient to obtain the opinion of the Supreme Court upon it, he may refer the question to that Court for consideration and the Court may, after such hearing as it thinks fit, report to the President its opinion thereon.

(2) The President may, notwithstanding anything in the proviso to article 131, refer a dispute of the kind mentioned in the said proviso to the Supreme Court for opinion and the Supreme Court shall, after hearing as it things fit, report to the President its opinion thereon.

ANS#2:

Advisory Jurisdiction

The Supreme Court has special advisory jurisdiction in matters which may specifically be referred to it by the President of India under Article 143 of the Constitution.

This power implies Court's right to give advice, if sought. Under advisory jurisdiction, the President of India may refer any question of law or public importance to Supreme Court for its advice. But the Supreme Court is not bound to give advice. In case, the advice or the opinion of the Court is sent to the President, he may or may not accept it. The advice of the Court is not binding on the President. So far, whenever the Court has given its advice, the President has always accepted it. The Court refused to give its advice on the question whether a temple existed at the spot, where Babri Masjid was built at Ayodhya.