The original practice, from what I understand, was that kohanim would bless the congregation every day during the amida of shacharis (and of musaf and n'ila when they were said, and of mincha on a fast day). At some point that changed, so that Ashk'nazim outside Israel now do so only on holidays and only during musaf. (S'faradim do it daily, and the practice in Israel is to do it daily, except in some northern cities of Israel.)
When did this change? That is, when did Ashk'nazim outside Israel stop the daily practice? And if S'faradim or Israelis also stopped it but later reinstated it, when did those occur?