Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Oakland, California to Cologne as you normally would.
It’s generally more expensive to depart on a Friday, if you have to leave on this day you can still search on Cheapflights to find great options that meet your needs.
Flights from Oakland, California to Cologne lean towards being more expensive in December. Prices are generally better when you fly from Oakland, California to Cologne in April, with the cheapest ticket starting at $560.