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I have a question in mind. Let say I travel from country A to country B and in these countries, the time difference is about 10 hours. So when I reach to country B from country A, does that affect my age. I mean, can I say that if the country B is 10 hours behind the country A, so my real age doesn't get affected?

marked as duplicate by pnuts, JonathanReez, Ali Awan, Karlson, JoErNanO Dec 16 '16 at 14:16

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    Do you mean legally, or physically? – CMaster Dec 8 '16 at 8:39
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    Yes, you become older and wiser. – JonathanReez Dec 8 '16 at 9:35
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Your age is judged according to to the local time.

So if you're born in Australia and travel to the US a day before your 21st birthday then it doesn't matter that the clock has hit midnight making you 21 in Sydney, you can't (legally) start getting drunk in San Francisco.

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    It is not only local time, but also local regulations dependent. E.g. the "legal" age for driving a car, alcohol, tobacco, sex, etc. is always determined by local law. Not by the laws of your home nation. Something completely legal in your home country could be underage and get you in serious trouble in another country. – Tonny Dec 8 '16 at 10:30
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    I mentioned it because I know from past experience some people really don't get that. Had to stop a 19-year old friend once, from trying to buy alcohol in the USA. (Legal age is 18 where we are from.) He kept saying, but I'm over 18... He just didn't get it that it doesn't matter when you are in a "legal age is 21" state and he got sufficiently angry towards the shopkeeper that the shopkeeper was about to call 911. – Tonny Dec 8 '16 at 10:46
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    What is not obvious is that these laws also apply to the nationality of the carrier used to make the trip. If the (almost) 21 year old was to fly Qantas they can get drunk on the plane on the way over. But if they fly Delta/American etc they will be refused service and have to stay sober. I once saw that happen to some not-so-happy 18 year old Australians flying from the US back to Oz. – Peter M Dec 8 '16 at 15:30
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    @theotherone, they get into trouble for transporting alcohol over the border? – o.m. Dec 8 '16 at 16:14
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    @theotherone, that can happen within a few homes and buildings straddling the border between Stanstead, Quebec and Derby Line, Vermont. – Dennis Dec 8 '16 at 17:08
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Legally: Yes it makes a difference, you can be of full age in one country, fly to another and not be of full age. However, this will rarely be the case. And it is reversal. Let's say you fly from A to B and you are 10 hours older, because in B it is 10 hours later, and you fly from B to A again you get 10 hours "younger" - from a legal point of view. So you cannot really accumulate it, +1 day is the maximum (you need to fly over the international date line).

More a curious point: When you fly, you will get old slower than the people on the earth who do not fly. This is the natural sciences point of view, based on the special relativity and we talk about differences of parts of a second. Please see this Wikipedia article if you are interested in a more detailed version. However, it is true. I remember an experiment where they flew with an atomic clock (most precise clock in the world) and afterwards there was a small time difference between the atomic clock which flew and the ones which stayed on the surface of the earth.

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    Interesting that you mention the relativity effect. While this is technically true, the effect is on the order of nanoseconds, so even if you fly every day, it won't make much of a difference. – drat Dec 8 '16 at 9:54
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    IIRC it's not even nanoseconds; only if you fly a ridiculous number of times it could ever reach a nanosecond. – Ramchandra Apte Dec 8 '16 at 10:24
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    @drat yeah I know it is not something effecting age in everyday life. However, I find it very interesting and if you are very picky it is in fact something to consider when you talk about getting older and flights ;) – Gnusper Dec 8 '16 at 10:53
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    It was calculated that for a pilot working for 40 years it would add up to ~ 0.000056 seconds ( 56 000 nanoseconds - or 56 microseconds ). Source. – Zitrax Dec 8 '16 at 10:54
  • @RamchandraApte, the individual effects are much bigger than that. This amateur experimenter measured a 20 nanosecond gain (relative to his near-sea-level home) from spending 2 days at 1500 meters on Mount Rainier. The computation for an airplane is more complicated because the time shifts from being high and going fast have opposite signs and partly cancel, but should be similar in magnitude. – Dennis Dec 8 '16 at 17:36

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