Ramadan will begin in the UAE on Tuesday, authorities announced.
The declaration came after the UAE's moon-sighting committee spotted the new crescent moon after sunset prayers on Monday.
The UAE's leaders wished all citizens, residents and Muslims across the globe peace and prosperity.
President Sheikh Khalifa wished leaders and their people good health and well-being, and further progress and prosperity for Arab and Islamic nations.
Sheikh Mohammed bin Rashid, Vice President and Ruler of Dubai, shared his best wishes for the month ahead.
“We wish the people of the Emirates and in the Arab and Muslim world a blessed month of Ramadan filled with mercy, goodness and blessings,” he tweeted.
Sheikh Mohamed bin Zayed, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the Armed Forces, said the occasion was a time for compassion and kindness.
"The Holy Month of Ramadan is now upon us and we welcome it with great joy. This is a time for patience, contemplation and compassion and we pray for God’s mercy and kindness," he wrote on Twitter.
Sheikh Dr Sultan bin Muhammad Al Qasimi, Ruler of Sharjah, and the Ruler of Ras Al Khaimah, Sheikh Saud bin Saqr Al Qasimi, delivered greetings to the President, Sheikh Khalifa, to mark the start of Ramadan.
They also sent warm wishes to Sheikh Mohammed bin Rashid and Sheikh Mohamed bin Zayed, and to all the Rulers of the UAE.
Sheikh Humaid bin Rashid Al Nuaimi, Ruler of Ajman, and Sheikh Saud bin Rashid Al Mualla, Ruler of Umm Al Quwain, sent similar messages to the UAE Rulers on the occasion.
Saudi Arabia's religious authority confirmed that Ramadan would also begin on Tuesday in the kingdom.
The start of Ramadan is determined by the sighting of the crescent moon, which is typically spotted using a telescope and then confirmed with the naked eye.
Spotting a new moon indicates that Sha'ban, the month proceeding Ramadan, has ended and the holy month has begun.
For the moon-sighting in the UAE, the International Astronomical Centre sets up telescopes on Jebel Hafeet in Al Ain, one of the country's highest mountains.
The committee deliberates over the data at the Ministry of Justice and, once confirmed, announces the start of the holy month.
This year, mosques will be open for prayer in the UAE during Ramadan, having been closed last year due to the Covid-19 pandemic.
Special measures are in place to protect worshippers and prevent the spread of the virus, including capacity limits and mandatory face mask use. Muslims are also asked to bring their own prayer mats and copies of the Quran.
Setting up iftar tables and distributing food in mosques is prohibited.
The elderly and people with chronic health problems have also been advised to pray at home.