The upside-down watch mystery 

I can't believe nobody made the 'Australia' joke just because the clock was upside down

In next weeks episode Tom will pose a question involving a slide rule and the symbols on a commodore 64 keyboard and truly confuse the rest of the panel.

Taha's answer of 6.5 hours is nearly just as valid. Rotating it once will advance the time 5.5 hours, and then rotating it again will advance the time 6.5 hours. Considering a full rotation most get the clock back where it started, the two times must add to 12, so there has to be a pair of answers. Some other thoughts I found interesting: the "nudging the hour hand" refers to the fact that you need to imagine the hour hand is 30 minutes back from where it is. This is due to the fact that clocks do not have continuous rotational symmetry. There are 11 times a day that have both hands pointing in the same direction. 12:00, 1:(60/11 minutes), 2:(2*60/11) minutes, etc. So, the clock hands have rotational symmetry every 11th of full turn. However, half a turn is not expressable as an integer number of 11ths of a turn, so, really an upside down clock is not a valid clock at all. If you also have a clock where the hours are marked (just the positions matter; ignore the values of the numbers), then the hour markings themselves have symmetry of a 12th of a turn, which is incompatible with the hand symmetry of 11th of a turn, therefore, there is only one valid marked clock orientation and that is right-side up. The obvious way to see the problem with half turns is to note that a clock that reads 1200 flips to have both hands facing down. But, wait, 30 minutes past the hour means that the hour hand should be between two hours too, not pointing directly at hour 6. While at first glance you might want to read both hands down as 630, the system Tom is referring to would actually read that as 530 (the rule being to nudge the hour hand back by half an hour, or, equivalently, if the minute hand is 30 or greater, read one hour less). Well, I suppose that's a fine system if you really want your watch flipping to work at 5.5 hour difference. But, you could also consider the hour hand to be the source of truth, which would give you 6 hour offset, and then just move the minute hand 30 minutes (just imagine it's pointing the opposite way). (So, when both hands are pointing down, pretend the minute hand is pointing up, and read the clock simply as 6:00). This has the appealing property that a half turn is half of 12 hours, both times you rotate the clock. Moral of the story: clock rotating is not as clean as you might expect going into it, mostly due to the redundant minute hand. If we used a clock with just an hour hand, you could rotate to your heart's desire. Edit: also, there absolutely are 24 hour watches and so Sabrina's answer of 12 hours could also be valid too.

I had a teacher that always wore an upside-down watch so when holding the book the kids would know what time it was just by looking at it 😅

BTW Korean here. Koreas don't use half time anymore. North Korea used UTC+8:30 since August 15th 2015(Korean independence day) while South Korea uses UTC+09:00. In May 5th 2018, North Korea returned to UTC+09:00.

I used to have a backwards clock. Agter a while it becomes just as automatic to tell the time on it; but its hilarious seeing how people react when they come to visit and try to see what time it is.

I'm pleasantly surprised that Tom can discuss timezones after his traumatic experience with them in the past...

Bonus question: What was the date that woman found in the arrivals lounge? India is always UTC+5.5. The time at Heathrow is UTC+0 for ~5 months of the year and UTC+1 for about ~7 months of the year. So the trick only works when the UK is on GMT between the last weekend in October and the last weekend in March. If you would like the riddle to work year round you can use Keflavik Airport in Iceland which is on UTC+0 all year. This also means Myanmar (UTC+6.5) works as and answer for Heathrow for more of the year then does India.

The fact Sabrina's camera is mirrored and the clock face is weird on its own makes this so much funnier.

A while back I designed Escape Rooms - one of them had a puzzle with wall analog watches in witch they had to use the time as a for digit code. You could not belive the struggle they had to get to the correct answer- no mather the age. Thank you for the ”brain candy” 🧠

Being from Pakistan, I Knew it would be India because as a kid I wanted to watch the show "young justice" but I always missed most of it, even when I rushed home, because it aired at "2:30" India but "2:00" PST, so I just assumed every country just went half an hour ahead from the last

I was born in 1997, so am too young to be millennial but too old to be Gen Z. I related to the slot machines in Scarborough but also not being able to read an analogue clock. This episode gave me a huge identity crisis 😂

I caught the "as stopped clock is right twice a day comment". By extension, a clock going backwards also reads the correct time twice a day. And the interval between instances of it being right get shorter the faster the clock is going. So logically, a clock going backwards infinitely fast is always right - but very hard to read.

You can actually use the mental nudging trick to also make it work for *Myanmar (not Korea) and Australia for UTC+6:30 (and for anyone wondering, the other country with UTC+5:30 is Sri Lanka; they do it to keep in lockstep with their largest trading partner and closest neighbor, similar to Samoa moving the International Date Line to be closer to New Zealand/Australia economically)

As an Indian, I knew the answer after Tom said difference is of 5.5 hours😌

This answer should totally be Australian, just so the watches can be "upside down" like the rest of the country :D

Interesting to see that Sabrina uses mirrored camera, meaning that her part of the screen shows everything mirrored, hence we see the upside down number XII as correct, although we should have seen the number as IIX (negative 8 if the Romans had known about negative numbers).

i actually figured this out quite quickly i feel like an absolute genius

I think it's adorable that these people say "digital watch" and think "Apple watch" . Ah, youth. According to Douglas Adams, once upon a time, people thought digital watches were a pretty neat idea. Apparently they still do, silly humans.

06:03 In Tom's defence, performing isn't that far from what he does in all those rallies.

To answer Tom's question, the Apple Watch does have accelerometers, but that doesn't rotate the display. What you do instead, is tell the wrist which wrist it is on, and which way and it'll adjust accordingly.

Their discussions around what a clock looks like upside down hurts me deeply lol

At 0:21 I thought Sabrina got it nice and quick - but the misunderstanding of how a clock works really threw me 😂 Don't know ho no one got it with that really close guess

The same trick works for travel from NL to AK! I never knew that but it's the same 5.5h. I'm guessing there aren't as many direct flights as from NL to AB.

Even as a not Gen Z person, it was interesting to think about a clock face again for the first time in quite a while.

love that sabrina and i made the same guess and mistake at the same time.

How To Read Clocks with Tom Scott

It's hard to make fun of people who make fun of themselves so well.

Won’t the watch show either a 5.5 or 6.5 hour difference depending on whether in the first or second half of the hour?

noticed Tom said you had to nudge the hour hand a bit. Think about it if the clock reads exactly 12 o’clock that is both and point to the 12 can you turn it upside down it looks like both has appointed to the sixth and that never happens it’s one of the forbidden positions o’clock hands, in fact, you should be able to tell if a clock is upside down by looking at the weather for the position of the hour hand and the minute hand, even if the numbers were removed.

The immediate thought I has was of nurses who used to wear an analogue watch upside down hanging from a ribbon at the top of their blouse/ apron. This had two obvious benefits: - the more buxom the lady, the easier it was for her to read the watch; - he/ she never had to worry about a wristwatch carrying germs from one patient to the next because of how difficult they are to clean on top of doing hands every 5 minutes.

This also appeared on an episode of QI, where Stephen Fry demonstrated this with his watch.

The Apple Watch does have a feature to change the direction of the face - for left or right handed users.

I'm not older than the answer in progress crew and I can read an analogue watch, which made it kind of surprising that they took so long to figure it out.

Small correction! Korea currently does not have half-hour time difference. North Korea was on UTC+8:30 for a while in mid to late 2010s, but they are now back to UTC+9 and South Korea has been consistently on UTC+9 for more than 6 decades now.

Got this straight away, but I am obsessive about time zones. It was deliberate, then we went and ruined by adding daylight savings time

The Watch will flip upside down but you have to tell it in the settings which wrist you wear it on and which side you have the crown on.

I heard this decades ago. I thought this was fairly well known.

My parents returned from their holidays in India just last week, so soon as the five and half hour was mentioned I guessed India.

I often will turn my watch upsidedown (or put it on the other wrist) in lieu of tying a string on my finger to remind me of something.

Not sure the question mentioned it was winter - during the summer months India is 4 1/2 hours ahead.

I always wear a watch, so I could look at my own watch for this, which made me figure out the half hour thing. I didn't know what countries have it, but I did remember there are countries with a UTC-offset that isn't just a whole hour... (Also, looking at your own watch upside down is uncomfortable.)

When it said "upside down" I was expecting it to involve the pin and wearing the watch on the left arm. There are left handed watches with the time adjusting pin on the LEFT side, so that the watch can be worn on the RIGHT arm. For ignorant right handers who can't figure out why, it's so that the watch doesn't catch on the table or other things as a left handed person uses a pen or a pencil.

I kept thinking it was a novelty 24 hour analog clock

It kind of changes the time by 5 and a half hours I think, which would mean she'd be from India. The hour hand is off by half a sector. It could be read as 6.5 hours to because of little hand being half an hour off but no-one works on British time + 6.5

So, in the during the clock change or daylight saving time, the upside-down watch can tell UK time and Myanmar time.

a few of the more significant assumptions made by this riddle, each one of which i think is enough to make it an invalid or "bad" riddle: - the minute hand, not hour hand, is exactly correct on the resulting watch face. this creates an ambiguity wherein: - the hour hand misaligned by 15° is assumed to be running ahead (as in India), not behind (as in Myanmar) - someone at Heathrow Airport is native to London, or to the GMT time zone generally (Heathrow is in this time zone for about 43% of the year; about one-third of travellers at Heathrow are connecting) - the analogue watch in question reads 12-hour time, rather than 24-hour or any alternative time representation methods - the watch is set correctly and the wearer is knowledgeable about its correct orientation (it's not for fashion or as a covert signal) - the wearer somehow prefers turning the watch upside-down to simply setting it correctly for the new time zone. most watches allow you to set the time by turning the side crown - the wearer suffers from a severe skill issue in which basic maths cannot be used to tell time in two time zones at once

Afghanistan also has a half hour time difference and borders Pakistan, so I was a little surprised to hear that it was India, although that it definitely a more "major" country than Afghanistan.

She had been in The Upside Down?

🤔 never knew that.

But how can young people *not* be familiar with analog clocks? Aren't there public clocks on railway stations, church towers, municipal houses etc? Wouldn't you be seeing those every day, even if you yourself didn't have one?

My dad told me this thing is school in 2nd grade, turn the clock face upside down and you get London time.

Not quite true! Normal clock has the hour hand aligned with the hour marking when the minute hand is vertical up (->0/12) Upside down clock with minute hand vertically up (->6/30) will have the hour hand halfway between the hour digits. You will need to read the minutes with zero at the bottom, or just ignore the minute hand completely.

i'm starting to suspect that Melissa had never seen an analogue clock face up until this episode edit: typo

Smug mode because I knew what the answer was going to be before hearing the question

Afghanistan also has the time difference in half hour increments. But it wouldn't have worked in this situation as its 4 1/2 hours difference from GMT. The only reason I know this is because a friend of mine served in the RAF at Kandahar Airfield.

Also Ethiopia

So I had xclock running on another virtual desktop, changed there, and turned my laptop upside down, and realized immediately what happens to the minute hand :D

This whole episode seemed unfairly difficult for gen Z 😅

To change an analogue watch you just spin a tiny dial on the side... it's QUICKER than taking the thing off, putting it back on and then constantly trying to look at the weird numbers to tell the time... naaa, no point!! 🙂

Please post the footage of Sabrina’s cat!

They do make watches that have a 24-hour dial.

This is a towards the end guess but Isn't Afghanistan a country with a .5 hour timezone?

My guess (haven't finished the video): she was from Fiji EDIT: India? I still don't understand. EDIT2: Oh. It only works if you imagine the position of the numbers remain the same. So only the hour and minute hands get reversed.

Jokes on me! My watch has a 24 hour dial! Looking at it now, 19:30 becomes 8:00, if I take the hour hand to be ahead. So that's a 12 1/2 or 11 1/2 hour difference, if I did the math right. So, a 24 hour dial is flippable for the difference between mountain time in the United States and India?

wrong description

...but why did she not have any identification?

It´s a lazy person trick, when someone asks you the time you just show the watch and the watch face will be upright to the person🙃

So, was she Indian and visiting the UK, or British and visiting India?

How would they have known she was not from Nepal instead?

India!

I'm gen-z but i HATE digital clock

Performing is usually the right word for Narendra Modi, Tom😂

I used to wear my watch upside-down because I was qUiRkY and rAnDoM

I keep thinking this is a bit pointless. Like they still don’t know who she is or anything. They literally only know where she went

taha is pakistan??

There's no way to tell what country she came from since anyone can put their watch on upside down.

the zoomers just killing the olds with not knowing what an analog clock face looks like or the very common nickname for slot machine haha also, addendum, i think andy zaltsman on the bugle or one of his guests had mentioned this fact too having travelled to india.

today i learned that the brits spell the word "analog" differently than in the us

Fk, I computed UTC+06:30 and Myanmar even before Tom ended reading the question. Turning clock at angles is not an easy feat. I'm a PhD. You mean, _the security guard immediately calculated it correctly?_ Either 💯 believable, or I lived my life for nothing-I should have become a security guard, not an insecure grad...

Narendra Modi 🔥