As example, my Name and Last name will never be proven false. Also, that in 2019 year Brexit talk comes - never be proven false.
It could be claimed that both of those are based on formal systems of record, and both could be falsified due to a clerical error in the relevant system.
I don't know your life history, but, for example, it has happened that babies have been mistakenly swapped in the hospital so that two families bring up each other's child - in that case, your first and last name might be incorrect. Alternatively, your birth certificate could have been forged to conceal your original identity, and so-on. It does depend on how you define what the proposition is concerning your first and last name - is it the names you currently use, or your birth certificate names, or the names on some official record, e.g. tax, etc.? If different names are associated with you on some government record, or some web site, possibly due to an error, they could be falsified by comparison with your birth certificate - or potentially, the reverse could occur. IOW the status of your first and last names could be considered a legal question.
As for Brexit, the current year is defined as 2019, and the timetable for Brexit talks is defined as occurring in the lead-up to the March 29th 2019 deadline, so I'm going to say this one is true by definition - i.e. the timetabling of the talks involved a formal system...
But, it is conceivable that it might be discovered that, by some ancient error, the calendar is wrong by a few years, meaning the 'true' date is not 2019. In this case, Brexit talks in 2019 could be falsified, but we'd keep the 'incorrect' calendar dates for convenience.
If it's remotely possible, however unlikely, then one can't be certain it will never be falsified.
But in both those cases, the truth or otherwise depends on formal definitions.
Of course, the more vague the proposition, the less likely it can be either falsified or shown to be correct, which is the problem with prophesies...
It's an interesting exercise - what do you think?