A slightly heretical thought here.
Is “Double Time” even necessary in Star Trek: New Frontier continuity anymore?
If you ignore the reference in Double or Nothing to the Dominion War being over, and treat that novel as following immediately on the heels of Once Burned‘s framing story, then New Frontier continuity lines up roughly where it needs to in order to match up with the Gateways story.
If Selar became pregnant in Fire on High and gave birth nine months later, if Fire on High takes place in the initial days of the Dominion War conflict, that puts Xyon’s birth in Dark Allies as being roughly contemporaneous with the end of DS9‘s sixth season or the beginning of the seventh.
If the Excalibur were destroyed at that time, if Calhoun were stranded on that backwater world for several months, that carries us until near the end of the Dominion War, and matches up with Xyon’s age, of eight or nine months.
So, the Excalibur-A could have been commissioned slightly before the end of the Dominion War, and that puts us four months (roughly) before the Gateways crisis. Which would be when Calhoun and Shelby take time out and go on their honeymoon.
The times as given in New Frontier work, without “Double Time.” With “Double Time,” everything from Double or Nothing onwards–Selar’s pregnancy being the major issue–is crammed into a three month period.
So, do we really need “Double Time”? It’s an interesting story, with lots of moral shadings that cast Calhoun in an unfavorable light, and has simply fantastic artwork, but the final page of the story with its sixteen-month time-jump creates a chronological conundrum.