Ruling Authorities for (Modern) Greece [solved]

First Hellenic Republic (1828–1832)

Kingdom of Greece (1832–1924)
- Otto (1832-1862)
- George I (1863-1913)
- Constantine I (first) (1913-1917)
- Alexander (1917-1920)
- Constantine I (second reign) (1920-1922)
- George II (first reign) (1922-1924)

Second Hellenic Republic (1924–1935)

Kingdom of Greece (restored) (1935–1967)
- George II (1935-1947)
- Paul (1947-1964)
- Constantine II (1964-1973)*

Regime of the Colonels (1973 (1967)–1974)*

Third Hellenic Republic (1974–today)

* Constantine II was officially the King of Greece between 1967 and 1973 but was not acting. Instead, the Military Junta was actually in charge since 1967 after the coup d'etat. The monarchy was officially abolished in 1973.

Sources:
1. https://en.m.wikipedia.org/w/index.php?title=Timeline_of_modern_Greek_history#/search
2. https://en.m.wikipedia.org/wiki/List_of_kings_of_Greece

I just added all four periods - three Helenic Republics and Regime of the Colonels. Crowned heads shall follow (hopefully) soon. You and all others are now free to start creating requests.

And now they are all up!

Thanks