Use 'hitherto' to refer to a period extending into the past, up to the current point or event discussed. His hitherto spotless reputation was now under scrutiny.
Pro Tip 2/3
Formal Tone
'Hitherto' often appears in formal or academic texts rather than casual conversation. The hitherto accepted theories are now being questioned.
Pro Tip 3/3
Emphasis on Change
Use 'hitherto' when emphasizing a change from past to present, particularly when introducing newly discovered information. This hitherto unexplored area offers great scientific potential.