A spokesperson of Delhi's Jama Masjid said as the moon was not yet sighted, the fasting won't begin tomorrow.
Sehri, which is the pre-dawn meal eaten by Muslims who keep fast, will begin tomorrow night.
Ramzan is the ninth month of the Islamic calendar. The month ends with Eid ul-Fitr and depending on the calender it lasts either 29 or 30 days, with again the sighting of the new moon.
During this month Muslims abstain from food and water from sunrise to sunset and join mass prayers at mosques.
This annual observance is regarded as one of the five pillars of Islam.