ST PETERSBURG, RUSSIA - JANUARY 6, 2017: A Christmas liturgy at the Kazan Cathedral. The Russian Orthodox Church celebrates Christmas according to the Julian calendar. Peter Kovalev/TASS (Photo by Peter Kovalev\TASS via Getty Images)

ST PETERSBURG, RUSSIA - JANUARY 6, 2017: A Christmas liturgy at the Kazan Cathedral. The Russian Orthodox Church celebrates Christmas according to the Julian calendar. Peter Kovalev/TASS (Photo by Peter Kovalev\TASS via Getty Images)