What will happen will be a court challenge, Christmas Day, Good Friday and News Day being Christian holiday and stat holidays. Courts will side with Moslems and Jews.
This is the end result of diversity it does not work. 
What they could do is give a voucher to everyone and you pick the holiday u want.
Christmas, Easter and New Years will be a regular day. New Years is based on Christ.
BC is before Christ and AD is after After death. Islam calendar is based on their prophet and i believe the year is 800 ad after his death.