Hey Antony, we tried to explain it in article above. There are several factors involved and usually it means a day or two difference; Situations like this year are rare. However, we do not believe that we calculate better than others – we simply tried to adopt the method that would be most biblical, but perhaps we do not do it best. We join spiritually with all those who seek to commemorate the death of our dear Savior. It doesn’t matter for us whether they did it now or will do it in a month. May God bless the purification and spiritual growth of each of us. Glory to God and glory to Jesus.