How does the CBP/CIS know the time of absence?

[coody]

How does the CBP/CIS know how much time an LPR is absence from the USA at a port-of-entry, a reply from the PR?

[Jackolantern]

They don't know 100%. Sometimes they look in your passport for the stamps of other countries. Sometimes they get traveler lists from the airlines (every airline is required to provide a passenger list to the DHS). Other times they have no idea.

[max2k1]

Originally Posted by coody

How does the CBP/CIS know how much time an LPR is absence from the USA at a port-of-entry, a reply from the PR?

Every time you leave the US (and when you come in), the airline submits a passenger manifest.
They have your passport details, personal details and in case of some airlines GC details.

That is sufficient to identify your departure. When you come back, your GC gets swiped and that records your arrival (plus the stamp they place)

and like JackO said, stamps in the PP from other countries would help with this as well.

[hopeofgc]

Originally Posted by max2k1

Every time you leave the US (and when you come in), the airline submits a passenger manifest.
They have your passport details, personal details and in case of some airlines GC details.

That is sufficient to identify your departure. When you come back, your GC gets swiped and that records your arrival (plus the stamp they place)

and like JackO said, stamps in the PP from other countries would help with this as well.

What happens if a person travels via drive through border from US to Canada? I mean that person has US PR and show the US PR card at Canada Port of entry.
I am guessing there is no way USCIS would know the absence of that person and for how long.

[Jackolantern]

Like I said before, they can't know 100%. They know in certain cases depending on how you entered or left the country, and they can do other intelligent guesswork based on passport stamps and other information, but not every port of entry/exit captures complete information about everybody leaving and entering.

Whatever they know, you don't know how much they know.