I was asked this question and researched the DL site which states 5 days prior. That said, is it 5 days from flight time, or a 5 day window starting at midnight the day prior?

Upgrades (when they used to clear!) typically cleared in the 5pm ish timeframe the day before the window. Given the changes to Gold and access to E+ at a premium, it makes the timeframe of "when" to go online and get access to E+ as a gold critical.

Can someone answer this question?