Because it is always today.
Today is never a good day to die. There is never a good day to die and everyone dies when their time comes.
Hodie die bonum cadere est.
You can make one.
"Today" in Latin is hodie (a contraction of hoc die, "on this day"). It's always an adverb. The corresponding noun is actually the noun phrase hodiernus dies ("the day of today").
Today Is a Good Day was created in 2009-09.
It's going to be a good day today
good
Today will be a good day = יהיה יום טוב (yee-YEH yom tov)
A Good Day for Love to Die was created in 2010.
A Good Day to Die was created on 2007-12-29.
Heute ist ein guter Tag zum Sterben is the German translation.
"Today is a good day!" in English is Oggi è un bel giorno! in Italian.