Many Ukrainian Orthodox Christians are preparing to celebrate Christmas on 25 December for the first time this year.
Ukraine has traditionally used the Julian calendar, also used by Russia, where Christmas falls on 7 January.
In a further shift from Russia, it is now marking Christmas according to the Western - or Gregorian - calendar, which it uses in everyday life.
Ukrainian President Volodymyr Zelensky changed the law in July, saying it allowed Ukrainians to "abandon the Russian heritage" of celebrating Christmas in January.
In a Christmas message issued on Sunday evening, Mr Zelensky said all Ukrainians were now together.
"We all celebrate Christmas together. On the same date, as one big family, as one nation, as one united country."
In the capital Kyiv, married couple Lesia Shestakova, a Catholic, and Oleksandr Shestakov, who is Orthodox, are celebrating Christmas together.
The pair - who until now marked Christmas twice, with their respective parents - attended the Sunday morning service at the city's Catholic cathedral (pictured above).
"There is finally a day in Ukraine which my husband and I can spend together in the cathedral and thank God that we are together, alive and in good health," Lesia told Reuters news agency.
The Orthodox Church of Ukraine (OCU), a newly created independent church that held its first service in 2019, has also changed its Christmas date to 25 December.
It formally broke away from the Russian Orthodox church over Moscow's annexation of Crimea in 2014 and its support for separatists in eastern Ukraine.
People prayed and lit candles across the country on Sunday.
In the western city of Lviv, which has been little damaged by the war, children in traditional costumes sang carols and took part in festive processions on the streets.
Ukrainians decorate a Christmas tree near the Independence Square in Kyiv, Ukraine
In recent years many worshippers have joined the OCU but millions still follow the historically Russia-linked Ukrainian Orthodox Church (UOC), and so will continue to celebrate Christmas on 7 January.
The UOC says that in 2022 it split from Moscow because of Russia's full-scale invasion of Ukraine although many people remain sceptical.
And of course there are expected to be quite a few Ukrainians who will be celebrating twice - the more the merrier.
