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I've never heard of such a thing before, but I'll take Bioguide's word for it, since it's an authoritative source. However, there's sometimes a discrepancy between Bioguide and the (equally authoritative) Clerk of the House about the beginning of service for members who win special elections. Bioguide sometimes considers it to begin the day of the special election, while the Clerk considers it to be when the member takes the oath of office, which is no earlier than the next day. I'm not sure which one is ""more authoritative"" than the other.   "