today vs now

today and now both are nouns.

Word	Noun	Adjective	Verb	Adverb
today	Yes	No	No	Yes
now	Yes	No	No	Yes

As adverbs, today and now are synonyms defined as:

Other synonyms of today include nowadays.

today (noun)	now (noun)
the present time or age	the momentary present
the day that includes the present moment (as opposed to yesterday or tomorrow)

today (adverb)	now (adverb)
on this day as distinct from yesterday or tomorrow	in these times
in these times	without delay or hesitation; with no time intervening
	used to preface a command or reproof or request
	at the present moment
	in the historical present; at this point in the narration of a series of past events
	in the immediate past
	(prefatory or transitional) indicates a change of subject or activity