The Splatoon Raiders crew creates its makeshift home base one month after the crash.
The opening disaster strands the mechanic and Deep Cut—Shiver, Frye and Big Man—on the Spirhalite Islands. Their helicopter is drawn toward the archipelago's center by a strange golden glow and storm-like clouds, forcing a crash landing. The story then jumps forward: in the month since the accident, the group has built a base called the Hideout Ship.
The Hideout Ship is more than a temporary shelter. It becomes the crew's operational hub while they search the islands for treasure and materials. The mechanic is sent out to gather supplies, encounters hostile local Salmonids and eventually repairs a derelict Exploration Bot. That machine helps locate treasure and can be piloted by a Deep Cut member.
The timeline is easy to confuse with the later exploration sequence, because Raiders begins after the crash rather than depicting every day of survival. “One month” refers specifically to the interval before the makeshift base is established and the main adventure gets underway—not the game's release date or a later mission duration.