I don't know about any other countries, but I think most holidays in the UK are completely secular. It would be utterly stupid to have a holiday dedicated to atheists - about as stupid having one dedicated to a religion. I don't think there will be any further holidays added to the calendar that have anything to do with religion. It's had it's day... even holidays which are/were religious are not celebrated as such anymore except by a few. I have yet to meet anyone who celebrates Easter because they literally believe Jesus was resurrected...