adverb
before now; so far; until now
Refers to the period up to the present moment; often used with present perfect or past tense in English translations.
これまでに一度も海外に行ったことがない。
I have never been abroad before now.
これまでに何度か彼に会ったことがある。
I have met him a few times so far.
Similar meaning, but 今までに emphasizes 'up to this very moment' more strongly, while これまでに can refer to a slightly broader past period.
Without に, これまで is a noun or adverb meaning 'until now' in a general sense, often used as a topic or in negative sentences. これまでに specifically marks a time boundary for an action or event.
Compound of これ (this) + まで (until) + に (particle marking a point in time). The kanji forms are ateji and rarely used.