Look at Indonesia's timeline carefully.

1670-1900 — Dutch colonists reigned Indonesia under one government: the Dutch East Indies.

1883 — Volcanic eruption of Krakatoa (Krakatau) island caused a devastating tsunami.

1928 — A youth conference pledged to work for "one land, one nation, and one language" for Indonesia.

1942 — Japan invaded the Dutch East Indies.

1945 — After the Japanese surrendered, nationalist leader Sukarno returned from internal exile and declared independence.

2021 (now) — Indonesia celebrates Independence Day on August 17th and the Youth Pledge Day on October 28th

Source: www.bbc.com

Krakatoa island ... in 1883.