1882
Milo James Thatch is born in Fishkill, New York to Augustus and Lucille Thatch.

1885 (3 yrs)
Augustus and Lucille Thatch are killed in a railway accident.

1890 (8 yrs)
Thaddeus and Milo Thatch go on a hiking trip. Milo finds an Indian arrowhead in a stream.

1893 (11 yrs)
Milo Thatch graduates from Buford Beaumont High School.

1895 (13 yrs)
Milo Thatch accepts (and declines) admission to Harvard, Yale, and Princeton Universities for advanced academic studies.

1896 (14 yrs)
Milo Thatch begins a tenure at Oxford University, earning a double doctorate in Linguistic Theory and Dead Languages.

1903-1904 (21-22 yrs)
Milo Thatch works as a Museum Linguist/Translator and Cartographic Restoration Expert in Washington D.C.

January 1905 (23 yrs)
Milo Thatch is briefly involved with a girl named Lisa McGrath.

1906-1908 (24-26 yrs)
Lyle T. Rourke leads an expedition to Bolivia and Peru under Professor Thaddeus Thatch to retrieve the Idol of the Sun.

1909-1910 (27-28 yrs)
Milo Thatch participates in an Academic Exchange Program, working in Paris at the Bibliotech National and the Prado Museum in Madrid.

1911 (29 yrs)
The Shepherd's Journal is retrieved by an expedition funded by Preston Whitmore and led by Lyle T. Rourke under Thaddeus Thatch. The crew includes Helga Sinclair, Dr. Joshua Sweet, Vincenzo Santorini, Manuel Ramirez, Wilhelmina Packard, Gaetan Moliere, and Jebidiah Farnsworth. The Journal is brought to Washington D.C. for study.

1914 (32 yrs)
Events of Atlantis: The Lost Empire.

Milo Thatch quits his job at the museum and is hired by Preston Whitmore.

A new expedition to Atlantis is launched, commanded by Lyle T. Rourke under Milo Thatch and funded by Preston Whitmore. The crew includes Helga Sinclair, Dr. Joshua Sweet, Vincenzo Santorini, Audrey Ramirez, Wilhelmina Packard, Gaetan Moliere, and Jebidiah Farnsworth.

The group travels to Atlantis using the Shepherd's Journal as a guide, losing over half the crew in the journey. Milo Thatch befriends Princess Kidagakash [Kida]. Commander Rourke discovers the whereabouts of the Heart of Atlantis and attempts to steal it. He kills King Nedakh.

Rourke is opposed by a mixed force consisting of members of the crew and Atlantean citizens led by Milo Thatch. Both Lyle Rourke and Helga Sinclair are killed in the fray. Atlantis is almost destroyed under a wave of lava which is halted by the power of the crystal. The surviving crew returns to the surface, keeping knowledge of their discovery confidential. Milo Thatch chooses to stay in Atlantis with Kida.

Taken from timeline here.