Start date, end date, and the case for leaving end date blank.

Every campaign in the Sponsored Ads console has a start date. Most have no end date and run indefinitely. Both fields look trivial; both have failure modes that we see in real accounts every month.

Start date — always today or in the future

The start date is when Amazon begins serving the campaign. Setting it to today means the campaign goes live the moment you finish setup; setting it to a future date queues the campaign. Two practical uses for a future start date:

• Event-bounded campaigns. A Prime Day campaign should start the morning of the event, not the day you finished setup.
• Launch sequencing. A launch budget that should not start until the ASIN goes live can be queued the week before, with a start date on launch day.

End date — leave it blank unless you have a specific reason

The end date is when the campaign stops serving. For always-on campaigns — your harvesting auto, your profitable manual, your brand defence — leave it blank. The most expensive incident we see in real accounts is someone setting an end date a year in the future, forgetting about it, and discovering twelve months later that the always-on brand-defence campaign has been off for two weeks while a competitor harvests the brand SERP.

Two cases where an end date is correct:

• Event campaigns. A Lightning Deal supporting campaign that runs for the 7-day deal week should end with the deal.
• Test campaigns. A two-week creative test should end with the test window. End dates are how you make sure tests do not silently turn into production.

The timezone trap

Campaign dates use the marketplace's local timezone, not your local timezone. A campaign with start date "1 December" on the German marketplace starts at midnight Berlin time, not midnight your-office time. For Prime-Day and BFCM campaigns this is a real issue — the marketplace clock can be hours ahead of or behind you, and your campaign will start hours before or after you expected it to.

Why the end date affects pacing

If you do set an end date, Amazon's pacing logic for budget rules and dynamic bidding behaves slightly differently: the algorithm knows the campaign has a finite window and will pace bids and budget across that window rather than treating each day as a fresh start. This is mostly invisible, but it is a real reason not to set arbitrary end dates on always-on campaigns — you are subtly changing how the bidder thinks about pacing.