Since creating that timeline, I had a longer look through Trail of the Sky Raiders (which is partly set in the Capital of the League of Suns) and discovered a couple of dates that seem to have been overlooked by everyone (as far as I can tell) since the adventure was published, and they don't seem to be in the Integrated timeline. The corrected timeline is below, the added dates are marked with a '*':
c. 308 Alzenei (Future capital of League of Suns) settled from the Spinward Marches. *
589-604 First Frontier War
615-620 Second Frontier War
819 - Worlds that later form the League of Suns break away from Dominion of Alntzar.
979-986 Third Frontier War
988 League of Suns founded *
1082-1084 Fourth Frontier War
1088 - Desaekhe begins Industrialisation.
1088 - 1103 Descarothe Hegmony expands
1105 Dispute between League and Hegmony
over Quarant
1107 Fifth Frontier War Starts (187-1107) (Legend of the Sky Raiders 347-1107)
1108 Crisis between League and Hegmony (Trail of the Sky Raiders 148-1108/Fate of the Sky Raiders 295-1108/The Stazhlekh Report 328-1108)