I'm working with my pharmacology colloqium (test) on Christmas eve ( 24th December) and reach my hostel around 7 p.m.. My 'teacher' available in her office till 9 p.m.. Surprise!! We don't have holiday on 25th December .
Yup, Russian didn't celebrate Christmas on 25th December since it is celebrate only by Catholics.
In Russia, the date is different because Russian orthodox church used the old Julian calender for religious celebration days. Hence, Russian celebrate Christmas on 7th January.