Documented via on-record university statement, as reported: The Harvard Crimson wrote on March 8, 2023, that university spokesperson Jason A. Newton confirmed Lieber retired from Harvard on February 1, 2023. The Crimson said he had been on paid administrative leave since being charged in 2020, and that Newton declined to comment on emeritus status.
Chemical & Engineering News later used the same February 1 date in its sentencing write-up. The Boston Globe’s sentencing story said he resigned in February. This site uses the spokesperson date (February 1, 2023) and the verb the Crimson attributed: retired.
Retirement is an employment fact. It is not the sentence. The sentence is April 26, 2023.