Conversion numbers change for days that have already finished. Why?

Nothing is broken. This is conversion lag, and it's the single most common cause of "the numbers changed" in Google Ads reporting. A conversion is credited to the day of the click, not the day it happened. Somebody clicks your ad on Tuesday, thinks about it, and buys on Friday - that conversion is added to Tuesday's row when it completes on Friday. So Tuesday keeps growing for as long as your conversion window is open. How long until a day is final depends on your own settings and your sales cycle. Short cycle ecommerce is mostly settled within a few days. B2B with a 30 or 90 day window can keep restating for months, and there is no point at which Google marks a day as closed. Two practical consequences worth telling the client: Any report you produce is a snapshot, not a fact. Put the date you pulled it on the report and you will never have this conversation twice. Never compare a fresh period against a mature one. Last week against the week before is not a fair fight, because the older week has had more time to fill in. If you want a trend, compare periods that have both had the same time to settle. We store whatever Google reports at the time of each update and re-pull recent days on every run for exactly this reason, so the history keeps catching up rather than freezing at the first value we saw.