ill-timed vs unseasonable

ill-timed and unseasonable both are adjectives.

Word	Noun	Adjective	Verb	Adverb
ill-timed	No	Yes	No	No
unseasonable	No	Yes	No	No

As adjectives, ill-timed and unseasonable are synonyms defined as:

Other synonyms of ill-timed include untimely, wrong.

ill-timed (adjective)	unseasonable (adjective)
badly timed	not in keeping with (and usually undesirable for) the season
	badly timed