CCCP007 wrote: ↑Sat Jan 11, 2020 3:22 am
how do they check the amount of days you've been out of UK for EU citezens,since they only look at the border at your Id and that's it
This is pure speculation but it is possible, at least when flying, that governments take note of the Advance Passenger Information (API) details that passengers give to airlines which includes the passenger's name, date of birth, and travel document details - pretty much everything they need to know.
I've heard that this information is passed to the destination airport authorities which I would assume includes border officials (possibly border officials at the origin as well). Airlines normally get penalised for transporting passengers that are unable to enter the destination country, so it would make sense that this information and the passenger's immigration status and/or right to enter are at some point before travel verified with the destination authorities.
As passenger attendance is also confirmed at the gate immediately before boarding it wouldn't be a huge leap to take note of this confirmation (or lack there of) and make an assertion that the person has (or has not) in fact left the origin country and is due to arrive in the destination country at said departure/arrival times respectively.
I also read somewhere that API data is also used at the automatic e-gates at border control so that the gates system knows who to expect and let through or, alternatively, deny entrance and require the person to go through the manual process with a border official.
As I said, all the above is pure speculation, but it's an incredibly easy way for border officials on either side to keep track of people leaving or entering the country.