Saudi Arabia's Supreme Court called on Muslims in the kingdom to watch for the crescent moon on Sunday evening, which would mark the start of Ramadan.
Whoever spots the Moon, whether with the naked eye or through binoculars, should report it to the nearest court and register their testimony, or ask the local authority in the area where they made the sighting to help them to do so, the Supreme Court said on Friday.
Searching for the new crescent moon can be difficult, because it is usually faint and is visible for only about 20 minutes.
Saudi Arabia said it expected Ramadan to begin on April 12 this year, although this early prediction would still need to be confirmed by a Moon-sighting.
If the Moon is observed over the kingdom on Saturday, the holy month will begin the next day. If not, it will start on Monday, April 12.
The Muslim world typically looks to Saudi Arabia when it comes to deciding the days on which major religious events fall, including the start of Ramadan and Eid Al Fitr, which marks the end of the holy month.
Meanwhile, the Saudi interior ministry announced a fine of 10,000 riyals ($2,666) for attempting to perform the Umrah pilgrimage during Ramadan without a permit.
Anyone caught attempting to enter the holy site of Makkah without a permit will be subject to a 1,000 riyal fine, a source at the ministry told the state Saudi Press Agency.