Until 2022, most Ukrainians, particularly Eastern Rite Christians, celebrated Christmas on January 7, like the majority of Orthodox churches. However, starting in 2023, Christmas has been officially observed on December 25.

The difference in Christmas celebration dates is due to the use of different calendars: the Julian and the Gregorian. The Julian calendar, introduced by Julius Caesar in 45 BCE, gradually fell behind the astronomical year (gaining a one-day difference every 128 years). In 1582, Pope Gregory XIII introduced the Gregorian calendar, which more accurately reflected the length of the year (by papal decree, the day following October 4 of that year was immediately October 15). This calendar was quickly adopted by Catholic countries, while Orthodox churches continued to use the Julian calendar. Meanwhile, the Gregorian calendar gradually became the standard for civil life in various countries, including Ukraine, where it was officially adopted in 1918. Thus, from 1918 to 2022, Christmas and other fixed religious holidays in Ukraine were observed according to the Julian calendar, which by then was 13 days behind the Gregorian calendar. Due to this discrepancy, secular and religious traditions diverged.

On September 1, 2023, the Orthodox Church of Ukraine (OCU) and the Ukrainian Greek Catholic Church (UGCC) transitioned to the Revised Julian calendar (a more precise version of the Julian calendar, which aligns with the Gregorian calendar until the year 2800). Since then, Christmas has been officially celebrated on December 25 according to the new church calendar, although some believers continue to follow the old Julian calendar, celebrating Christmas on January 7 (which corresponds to December 25 in the Julian system).

The transition to the new Christmas date was not abrupt: from 2017 to 2022, Ukraine officially celebrated Christmas on both December 25 and January 7, with both days recognized as public holidays. Parishes had the freedom to choose when to celebrate Christmas. Russia’s full-scale invasion of Ukraine in 2022 accelerated the process of Ukrainians, including Orthodox Christians, distancing themselves from Russian religious traditions. According to statistics, most believers supported the shift to celebrating Christmas on December 25. However, the church does not prohibit celebrating Christmas on January 7, allowing for a gradual transition among parishioners. Many people continue to celebrate Christmas on both dates—December 25 and January 7—combining both traditions.