Mavericks can't be Verified

This afternoon I tried to install OS X Mavericks on a Macbook Pro that had been sitting for a couple of weeks with a dead battery.

Every time I tried to install, it would tell me:

This copy of the Install OS X Mavericks application can't be verified.

(I didn't get a screenshot, so the wording might be slightly off).

The only Apple Support article I could find, says to check the date and time settings, but because I wasn't already running OS X, there's no easy dialog to set date and time (and connecting to a WiFi network didn't seem to fix it either).

However, Terminal came to the rescue. Simply set the current date and time using the date command. To make it even easier, you can simply use the command below (it will automatically update with the correct time in your current timezone).

date 0403210914