You might like to "add a time zone to your calendar."
This allows you to display 2 time zones, which will both show to the left of your calendar grid. While you are planning your CET trip, you can display that time zone. The CET entries will align correctly with the vertical CET timezone bar, while they'll be offset by 6 hours to your EDT timezone bar.
While you're in travel planning mode, you can keep both timezones displayed, or you can temporarily turn off EDT so that you only see CET. Then turn EDT back on when you're finished.
Add a time zone to your Google Calendar:
At the top, click the Settings (gear icon) and then select Settings from the menu.
On the left, click Time zone and check the Display secondary time zone box. (The primary time zone is where you live.)
Click the Secondary time zone field and select another time zone.
(Optional) To identify the time zone, add a label, such as Europe.
ETA: the steps above are for a laptop/desktop. If you're on your phone, use the same help page (as linked at the top of this reply) and follow the instructions on the tab for "Android" or "iPhone & iPad." On Android, you won't be able to display 2 timezones side by side, but you can easily switch back and forth, just as avirosemail descripted up thread.