Against the Tide of Years is a science fiction novel by Canadian-American writer S. M. Stirling, the second out of the three alternate history books in the Nantucket series.

In the Island in the Sea of Time, the island of Nantucket in Massachusetts is transported by an unknown phenomenon (called "The Event" in the series) on March 17, 1998 at 9:15 P.M. EST back in time to the Bronze Age circa 1250s BC (corresponding to the late Heroic Age of the Trojan War).

As the series progresses, it becomes clear to Nantucket's government that sitting back and adopting isolationism will only profit those renegades who, under the leadership of ex-Coast Guard lieutenant William Walker, have fled the island to exploit the Bronze Age peoples of Europe and the Middle East.

The leadership of the Republic of Nantucket has invested a great deal of time and effort into building up a substantial military force, both a deep-water navy and a Marine Corps, but the bulk of Nantucket's population are more interested in commerce and exploration than in bringing the renegade Walker to justice.

A sneak attack on Nantucket itself by the nation of Tartessos, led by an ally of Walker, unites the factions of the Republic behind an all-out effort to topple Walker's growing empire, centered in Achaea (Greece), in a two-pronged campaign, attacking Tartessos and opening a second front in the Middle East (through an alliance with Babylon, the Hittite Empire and Mitanni).