Historic Grand Prix of Monaco

The Historic Grand Prix of Monaco (also called the Monaco Historic Grand Prix depending upon the source) is a series of automotive races focussed on historic motorsport. The event is typically held biennially two weeks before the Formula One Grand Prix of Monaco.
History.
The first Monaco Historic Grand Prix was held in 1998, and has been held every two years since. With the beginning of the Monaco ePrix Formula E race, the Historic Grand Prix runs in even-numbered years and the ePrix runs in odd-numbered years. An exception occurred in 2020, where the 12th event was postponed due to the COVID-19 pandemic, instead taking place on April 25, 2021, two weeks before the Monaco ePrix and four weeks before the Formula One Grand Prix. 
The 2010 running of the event was the seventh in the series. It featured eight races total, in various historic motorcar categories:
By the 9th running of the event in 2014, the number of races had been reduced to 7, and there had been some tweaking of the categories, better to distribute the competition:
For the 11th running of the event in 2018 the number of races remained, the division into categories based on the year of manufacturing has been adjusted again. The following classes remained static for the 12th running of the event in 2021.