Each user gets to choose their own default timeRange.  Theoretically, a script might be possible, using the user api, but it's pretty deep in the code.  And, as soon as someone changes their timeRange for some other purpose, it would be changed for this dashboard as well.  That said, you can write a screen and set timeRange to a different time in additional context, such as last 7 days, but the it will be set that way for everyone who uses the dashboard.
hi, i create a new dashboard and i share the portal link but it defaults to 4 hours of data. i want it to default to 7 days. how do i change this for all profiles?   thanks!!!!  Scott.
6.8 vfog dashboard link question