May 21st in the Giro:
1919 Constante Girardengo took opening stage to Trento. In a
time of giants he would win 7 of 10 stages in that edition and
take the overall by 52 minutes.
By the late 1950s Spain was establishing itself as a force to
be taken seriously in the Grand Tours. This was evident on May
21st in the Giro:
1958 Federico Bahamontes - Turin
1959 Miguel Poblet - Naples
1960 Miguel Poblet - Campobasso
1961 Miguel Poblet - San Remo
1962 Angelino Soler - Panicagliora
1963 Jaime Alomar - Campobasso
Italian Vendramino Barivera broke the streak with his May 21st
win in 1964.
Marino Basso was a force in Italian sprinting in the early 1970s.
He took stage wins on this date in the 1970, 1971, and 1972 Giros.
May 21, 1976 was a double stage. Patrick Sercu took full advantage
of this by winning them both!
Freddie Maertens would duplicate this feat in 1977 on May 26th,
taking stages on that date. He also won in Avelino on the 21st. In
all he would take 7 of the first 11 stages that year in an amazing
display of sprinting superiority.
The 1987 Giro began on this date with a prologue in San Remo won
by defending champion Roberto Visentini. The next day saw a double
stage with a time trial won by Visentini's Carera teammate, Stephen
Roche. The tone of that Giro was set early.
The Merckx family had a lot to say about May 21st. Eddy won on
Novara in 1968, and Axel followed that up with a stage win in Prato
in 2000. I believe that is only such case of father/son stage wins
on the same date in Grand Tour history.