Facebook has two reporting modes:
Conversion Time Report: This is the time the pixel is fired (ie. the time the actual conversion took place).
Impression Time Report: This is the time the ad was shown, which is not necessarily the same time that the conversion took place.
An ad is shown to a user on the 2nd day of the month
The user clicks on the ad, visits the website, but takes no action
They come back and convert 3 days later
In this case, the impression time for this conversion will be the 2nd, but the conversion time will be the 5th.
You can easily switch between modes by using the "Report Mode" button. Please note that Facebook reports on Impression Time by default. So, there could be discrepancies between Facebook’s report and Adphorus’ Conversion Time report. However, lifetime performance report data should ultimately match.