至今 (zhì jīn) is an adverb meaning 'so far, up to now, to this day', used in both speech and writing to emphasize a continuing situation from the past. It is more common and flexible than the formal, written 迄今 (qì jīn), which is mostly found in literary or official contexts. 至此 (zhì cǐ) means 'up to this point' and refers to a stage or event, not a time span.