taru-adjective, adverb taking the 'to' particle
Describes a calm, unhurried state or atmosphere, often with a positive or neutral tone. Used as a たる adjective (安閑とした) or adverbially (安閑と).
彼は安閑とした態度で仕事をしている。
He works with a relaxed attitude.
休日は安閑と過ごしたい。
I want to spend my day off leisurely.
taru-adjective, adverb taking the 'to' particle
nonchalant; unconcerned; carefree
Implies a lack of concern or urgency, often in situations where one should be more attentive. Can carry a slightly negative nuance of being too relaxed when action is needed.
緊急事態にもかかわらず、彼は安閑としていた。
Despite the emergency, he remained nonchalant.
安閑と構えている場合ではない。
This is no time to be sitting around carefree.