na-adjective
Describes things that are ordinary, part of daily life, or not special. Often used to contrast with extraordinary or exceptional situations.
彼は日常的な出来事を日記に書いている。
He writes about everyday events in his diary.
この問題は日常的によくあることだ。
This problem is a common, everyday occurrence.
普段 is a noun/adverb meaning 'usual' or 'ordinarily', often used for habitual actions. 日常的 emphasizes the everyday, routine nature of something.
Formed from 日常 (daily life) + 的 (-like, -ish), a common suffix for forming adjectival nouns.