Sejong the Great

Every entry, with its source

At 0

1. May 15, 1397

   Born the third son of King Taejong

   Date converted to the Gregorian calendar.

   Source: en.wikipedia.org

At 11

1. c. 1408

   Given the title Prince Chungnyeong

   Around age 11.

   Source: en.wikipedia.org

At 21

1. Sep 1418

   Named crown prince over his brother, king two months later

   Age 21. His father Taejong held the military as retired king.

   Source: en.wikipedia.org

At 23

1. c. 1420

   Founds the Hall of Worthies

   Around age 22. He gathers scholars and grows it into a research institute.

   Source: en.wikipedia.org

At 37

1. c. 1434

   Builds a sundial and a self-striking water clock

   Around age 37. He promotes engineers such as Jang Yeong-sil.

   Source: en.wikipedia.org

At 44

1. c. 1441

   Builds a rain gauge

   Around age 44. The first standardized rainfall gauge anywhere.

   Source: en.wikipedia.org

At 46

1. Dec 1443

   Creates Hunminjeongeum, the Korean alphabet

   Age 46. The twelfth lunar month of 1443.

   Source: en.wikipedia.org

At 49

1. Oct 9, 1446

   Promulgates Hunminjeongeum

   Age 49. Korea marks this day as Hangul Day.

   Source: en.wikipedia.org

At 52

1. Apr 8, 1450

   Dies at 52

   Source: en.wikipedia.org