Halo Wars only spans a few days even with Slipspace travel. Going by the books, that means that Harvest, Arcadia, and the Shield World are all in the same solar system.

: According
: to Grim's summary of the battle on Alpha Halo, the first three missions
: were undertaken all within the same day. Of course I could be ignoring
: time zones where Truth and Reconciliation is orbiting a far off part of
: the ring in the early morning or at night. But the next four levels, at
: the Silent Cartographer to the Library, all happen across the span of a
: single day in three unique environments likely spanning hundreds or
: thousands of kilometers in distance from each other.

We knew from The Flood that Halo: Combat Evolved took place in the span of just over 72 hours. It makes sense for the events in The Flood, as I cannot imagine any force from the Pillar of Autumn holding out much longer if they holed up in a single defensible position. They're outnumbered, outgunned, and the Covenant have air superiority.

Also: how is night and day handled on a Halo? You've have night when the gas giant eclipses the local sun, when your slice of the ring is facing away from the sun, and when a far section of the ring eclipses the sun.

How regular would that be?