The age limit on electors became effective on 1 Jan 1971 (Ingravescentem Aetatem). The limit of 120 electors was added on 1 Oct 1975 (Romano Pontifici Eligendo). The current rule (cardinals age 80 or less on the day the Holy See becomes vacant may vote) was added on 22 Feb 1996 (Universi Dominici Gregis).
Before the 1996 language, it is not possible to precisely say the number of cardinal electors (it was based on when the conclave began), so I'll disregard the 2 times before then when the number could have been 121 for short periods.
Since then, there have been 10 times when the 120 number was exceeded.
There are two entries beginning in 2003 due to Cardinal Gulbinowicz. At the time it was thought that his birth year was 1928 (age out in 2008), but in reality it was 1923 (age out in 2003 just before the consistory). The correct birth year was not acknowledged until February 2005.
1) in reality
2) as perceived at the time
3) the final period is an estimate that assumes no cardinal elector dies and no new ones are created before the end date.
For completeness, here are the other times when the 120 limit was exceeded with some notes.
1) This was before the age limit and the 120 cardinal elector limit existed.
2) The count and Days are based on the current language. At the time the age limit was more vague and a precise count of electors is not possible.
(Revised on 27 Aug 2018 to add info about Cardinal Gulbinowicz)