Questions tagged [time]
Puzzles which include the concept of time, as for instance: clocks, dates, calendars, conversions from one time zone to another, time-intervals.
84
questions
13
votes
3answers
2k views
A stopped watch shows correct time ---
You know the old saying
A slow or fast running watch is worse than a stopped (broken) watch. At least the stopped watch shows correct time twice a day!
Here is a challenge:
A person was wearing a ...
3
votes
1answer
164 views
Lazy Box Sorting
In front of Louis there are 10 boxes containing different foods: tomatoes, (red) herrings, and bananas.
The boxes are arranged side by side in a line. Right next to the last box are three bigger ...
6
votes
5answers
1k views
Probability of three identical digits on a four-digit digital clock?
On a digital clock showing 00:00 to 23:59, what is the probability of having exactly three identical digits?
11
votes
0answers
288 views
The Odd Street Clocks
The clockmaker took a walk after a lunch from a restaurant and across the block corner he found the old clock box with four similar looking clocks on every wall. It is in the middle of the street ...
1
vote
2answers
143 views
Measure nine minutes with two hourglasses [duplicate]
How can you measure 9 minutes with a 7-minute hourglass and a 4-minute hourglass?
Note: In this question it states where it's possible or not but not the actual procedure for this exact situation.
7
votes
2answers
424 views
Puzzle - Counting Lights, Not Sheep
Some nights it is difficult to get to sleep. On one such night, John counted the
number of LEDs (Light-Emitting Diodes) on his clock radio that was on to make
each individual time from 10:00 PM to 12:...
-1
votes
1answer
173 views
A sensitive lent
The number of days from the first day of Lent to the last day, inclusive, may be best described by:
a) XL
b) Xl + VI
24
votes
1answer
983 views
Using burning ropes as timer - how to measure 1 hour and 8 minutes with 3 ropes?
This is a variation of a well known puzzle, you can find the other versions on PSE.
You have three ropes and a box with ten matches.
As usual each rope takes one hour to burn completely when lighted ...
-4
votes
3answers
128 views
Previous palindrome date
2nd of February this year will be a palindrome date, because 02/02/2020 reads the same forwards and backwards. But when was the previous palindrome date?
5
votes
1answer
234 views
Why do I celebrate later? (still 13,37 years)
A very little time ago, just a bit ago one may say, people started partying. Some even went out of their houses to do soā¦ crazy thing, IMHO.
Anyway, I don't, I'll start partying in 4886 days.Ā¹
Why do ...
4
votes
1answer
348 views
Using burning ropes as timers
This puzzle is an harder version of a very famous one.
It has been asked many times on PSE, but this time the question is slightly different (1) (2). So please read this question twice before marking ...
1
vote
1answer
101 views
Date from 2 wooden cube puzzle [duplicate]
In an interview the interviewer asked me a question based on date.
Suppose in a office, at the manager's desk there are 2 wooden cubes to show the date of month, every day the manager sets the cubes ...
6
votes
7answers
4k views
If the second hand goes backwards, starting from 12:00, how long does it take to meet with the minute hand?
If the second hand of a clock goes backwards, starting from 12:00, how long does it take until it meets with the minute hand (which is going forwards)?
0
votes
2answers
345 views
Witches' Coffee [closed]
Two witches make a nightly visit to an all-night coffee shop. Each arrives at a random time between 0:00 and 1:00. Each one of them stays for exactly 30 minutes. On any one given night, what is the ...
3
votes
1answer
267 views
Infinite dials to reset ever?
I have an infinite number of dials with red needles that rotate $n\in\mathbb{Z^+}$ times every second. They all start pointing North.
Will they simultaneously all point North ever again?
6
votes
2answers
1k views
What's Bob's age again?
I created this problem myself, but I did have inspiration.
Today is a special day, I'm moving out of my parent's house. My father comes to me and says "Wow, you're half my age. On the day we moved ...
-1
votes
1answer
156 views
When was Sia born? [closed]
John was born on 15 August 2007. If Sia is 17 year older than John. On which day Sia was born?
Tuesday, Wednesday, Monday, Friday
4
votes
3answers
234 views
A Second Hand Question
" It is a very simple question", said Grandpa
" Look at that wall clock and tell me exactly how many times the
Second Hand passes directly over the Minute and the Hour Hands in a 24
hour period....
16
votes
5answers
679 views
You cannot have 120 degrees of separation, but how close can you get?
If you take a look at a standard three-hand gear-driven analog clock, there is never(see footnote) a time of day where the hands of the clock divide the face equally into 120 degree segments, but you ...
54
votes
12answers
12k views
A clock correct three times a day
A stopped clock tells the right time twice a day. How fast must a
clock go for it to be right three times a day?
10
votes
6answers
832 views
Short Puzzle: Graphic Painting
The artist in the market is giving this painting for free (the last one on his rack). I asked him if I can take it but he replied "Why should I give it to you?" The frame could be useful but I dont ...
4
votes
5answers
447 views
Time-Motion puzzle
Time and Motion studies are well established.
Here is an easy question:
It takes 8 men 6 months to build 2 houses at a cost of $50,000.
It takes 10 men 5 months to build 3 houses at a cost of ...
23
votes
3answers
2k views
Digital Clock Brightness
My alarm clock has a typical 7-segment digital display showing hours and minutes.
Every lit segment is equally bright, and every unlit segment is equally dark. The separator (:) is always lit.
...
11
votes
4answers
935 views
Mirrored clocks
Triangulating for the simplest puzzle that is still at least somewhat interesting to solve..
On the left side wall in this picture, we have two particular clocks:
1: an analog clock with identical ...
4
votes
2answers
802 views
What timezone am I?
It was 17:52 in the evening and I couldnāt wait for my class to finish. Only 8 more minutesā¦ I really hate night school!
I sat there pondering the stuff on the blackboard and wondering why he wrote it ...
4
votes
2answers
254 views
Switching the clock
"Observe the time, would you, Watson, old chap?"
I did as instructed and glanced at the large grandfather clock standing in the corner. "Just a little after 4.42, Holmes."
He nodded, "So when the ...
1
vote
2answers
255 views
What are the chances on watching the clock? [closed]
This is a relatively straightforward little puzzle, but the answers are somewhat unintuitive or can prompt a new perspective. It might be an interesting little puzzle for a probability teaching ...
-8
votes
5answers
424 views
A cowboy rodeo riddle [closed]
First, the cowboy went to the rodeo on Monday.
Three days later, he went back home on Friday.
Can you solve it?
17
votes
14answers
11k views
My birthday is uncommon
I was born 1 day after my sibling. Yesterday was my sibling's birthday but today is not my birthday.
When is my birthday?
30
votes
11answers
13k views
Born on the same day, but one is two years older
Two people were born on the same day, same year, and share the same birthday.
One is 2 years old, the other is only a few days old.
What's going on here?
9
votes
2answers
288 views
Where are you at this time
Where are you if,
When it's 10 o'clock, it's 2 o'clock
When it's 5 o'clock, it's 7 o'clock
7
votes
2answers
342 views
How many dates are ambiguous across the Atlantic?
The Day/Month/Year date system commonly used in Britain (and much of Europe?) and the Month/Day/Year system commonly used in the US can lead to confusion when, for example, we write 9/3/2018 for the ...
23
votes
1answer
1k views
Aging A Lot Faster
The day before yesterday, I was 20 years old, and next year I will turn 23. What day is it today?
Note: This is not lateral-thinking, and the solution is real and ...
10
votes
4answers
1k views
How to rephrase this puzzle about a meditating monk and incense
Here's a math-flavored puzzle I found on Andrej Cherkaev's website that I like to give to my undergraduate math students. I've paraphrased it to try to make it clearer:
A monk was instructed by his ...
3
votes
5answers
588 views
Curiosity of February 5$^{th}$
Some people write February 5$^{th}$ using the md format, as $2.5$ or alternatively as $2/5$.
Note that $2.5 \times \frac25 = 1$.
Is there any other date satisfying $a.b \times \frac{a}{b} = 1$?
...
9
votes
2answers
499 views
A Final Twins Puzzle: Twelve Days Difference?
Inspired by @athin's One More Twin Puzzle: Four Days Difference?
After reading @athin's question, I was inspired to ask my own puzzle club about their birthdays. One of the members, Ethan, surprised ...
13
votes
3answers
916 views
One More Twin Puzzle: Four Days Difference?
This is updated version for Another Twin Puzzle: Three Days Difference
Today is my first day joining my college's Puzzle Club. It is so much fun gathering in a group with similar interests! I meet a ...
11
votes
2answers
501 views
Another Twin Puzzle: Three Days Difference
Today is my first day joining my college's Puzzle Club. It is so much fun gathering in a group with similar interests! I meet a lot of new friends and of course asked their contact number to discuss ...
15
votes
2answers
563 views
“Musical chair” for clock hands
A colleague and me usually make bets on the time when a simulation is finished. Next time I would suggest the following: At the time the simulation is finished we take a look at the analog clock on ...
7
votes
1answer
260 views
11
votes
5answers
3k views
This puzzle is late!
I meant to release this puzzle 15Ā¼ hours ago, and forgot again just over 9ā
hours ago.
But don't worry, it's fine. The puzzle is finally out.
What is this puzzle about?
NB: What timezone I am in or ...
17
votes
1answer
2k views
Finally, you wake up from a coma
You can barely open your eyes when a doctor walks up to you:
You are a lucky one. Not many people have survived an accident like this. Only a handful of neurosurgeons are able to perform such an ...
-3
votes
1answer
92 views
Daylight And Standard Time Not Equal Timespan Yet Works Out [closed]
I have been thinking about this for a long time now, and no one can answer it. I forget the exact length span, however, the span for each is not equal. For example, DST is 120 days, and "standard" ...
6
votes
7answers
22k views
A man is born in 1955
(I heard this in a movie and I think itās pretty cool.)
A man is born in 1955. Today, the 14th of August, 2017, he is 18. How is this possible?
36
votes
5answers
9k views
Measure 22 minutes with 7 and 13 minute hourglasses
You have two hourglass timers. One can measure 7 minutes and the other hourglass timer can measure 13 minutes. This means that it takes 7 minutes for the sand timer to completely empty the sand from ...
6
votes
7answers
4k views
Full-sized ice cubes
On a table in front of you is a small freezer that is capable of holding seven standard ice cube trays stacked on top of each other. There are no shelves to separate the trays, and if you stack one ...
4
votes
3answers
590 views
The time is approximately 10:10
Watches in advertisements tend to be set to 10:10 (unless you're Apple). The reason seems to be that the hands are symmetrical when they're at 10:10.
Except they're not. The hour hand moves ...
3
votes
8answers
10k views
How many minutes is it before 12 noon? (tricky)
This puzzle is a one I met in an IQ test. I believe it's so tricky, however, the concept is quite simple.
How many minutes is it before 12 noon if 68 minutes ago it was three times as many minutes ...
1
vote
2answers
215 views
X past X, Y to Y
While sitting in the waiting hall a wall clock caught my attention. I realise there are only 15 minutes left for the conversation that will determine my path in life. I then took a glance at my watch. ...
7
votes
5answers
740 views
One a puzzle, two a puzzle, Hot Cross Clocks
It's Good Friday!
I want to make perfect hot cross buns by superimposing two 12-hour clock faces on top of each other. Is this possible, and if so, how many ways are there of doing so?
In other ...
