The difference between filtering by "Created At" Attribute and "Person Was Created" History

[Anonymous]

I was surprised to see some of our Smart List numbers change quite a bit, when filtered off the Created At timestamp, versus the activity history of the person being created... Can anybody clarify the difference between these two timestamps?

It seems as though maybe the Person Was Created history is triggered when the person anonymously is introduced to the system, but the Created At attribute is maybe driven off the form submission, but I can't say for certain. I do know that there are more people in my smart list when I filter by "Person Was Created" in timeframe Last Month, versus "Created At" attribute is in timeframe Last Month. 

[Anonymous]

I think the Created At stamp is for when a lead becomes known, as you noted, whereas Person was Created is the Anonymous lead tracking.

[Anonymous]

Thanks for the reply. Will let this sit here for a bit, but I suspect we are right... was hoping for a definitive answer, but appreciate the comment suggesting I was on the right track.

[Anonymous]

To the best of my knowledge, Lead Was Created filter is the date the record changed from an anonymous record to a known record. The Created Date field is the date the record was created in Marketo. This date can be different than the Lead Was Created date since the record could have been visiting the website and cookied weeks or months before it was converted from an anonymous to known record.