I assume that this is what this refers to? http://www.prague.net/blog/article/29/dusicky-czech-halloween
No, you need "the dead" in this sentence. If you were saying something like, "Today is the day of dead trees," where "dead" is an adjective directly modifying a noun, it would be fine without the article. But when "dead" is used as a noun, as it is here, it's just not right without the article.