Does it recognize the date and time stamp across multiple expense reports?
The time stamps will be consistent across multiple reports. I'm not sure if that answers your question though, so if not please rephrase with a bit more context and I'd be happy to take another shot at it!
Does the duplicate detection flag out an expense that was submitted already from another expense report?
It depends on the expense itself more than the report. If two expenses are SmartScanned on the same day for the same amount, they will be flagged as duplicate. We have more information on Duplicate Detection that you may find helpful at the link below.
Deep Dive: Duplicate Detection
If the same receipt was submitted twice on a different date, how would it be detected?
Sorry, that last response may not have been entirely clear. Duplicate Detection will look at all expenses in a single user’s Expensify account regardless of the date it is uploaded. As long as the date and amount match, then we will show a duplicate.