From my understanding, sometimes the writer/artist will choose certain kanji to better express a nuance they’re going for for some words, so it will be “said” one way (きょう), but will then assign a different, specific kanji to represent the word in writing (翌日)
So though they’re saying “today”, the nuance might be something you can only get my reading it and seeing that they use the kanji 翌日 to represent it, so they might actually be referring to something occurring the following day – but since I don’t know the context, I’m not entirely sure if this interpretation fits!
I also found this explanation on stackexchange that goes into a bit more detail about it, it’s basically a stylistic trick writers can utilize in written Japanese text to say one word, but provide an implication of something else by assigning a different kanji to the word
Example from the site:
Meaning: “You can’t be trusted”
They’re saying “おまえ/you”, but chose to use the kanji 泥棒 to represent it to give a nuance that “You can’t be trusted (because you are a thief)”