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.

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1
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2answers
137 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.
6
votes
2answers
403 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:...
5
votes
3answers
10k views

Finding Day Puzzles

When the day after tomorrow becomes yesterday, the day which would then be today will be as far from Sunday as the day which is yesterday when it's two days after that day's tomorrow. What day of the ...
-1
votes
1answer
163 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
951 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 ...
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)?
-4
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3answers
125 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?
4
votes
1answer
336 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 ...
5
votes
1answer
232 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 so… crazy thing, IMHO. Anyway, I don't, I'll start partying in 4886 days.¹ Why do ...
1
vote
1answer
96 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 ...
16
votes
5answers
602 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 ...
10
votes
6answers
829 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 ...
0
votes
2answers
260 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 ...
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 ...
4
votes
3answers
226 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....
3
votes
1answer
263 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?
-1
votes
1answer
153 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
15
votes
2answers
552 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 ...
55
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?
8
votes
5answers
20k views

Meeting of hands on a clock

We have a regular analog clock with three hands - second, minute and hour. On a given day, how many times do: (a) the minute and hour hands (b) the minute and second hands (c) the hour and second ...
4
votes
5answers
444 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 ...
11
votes
4answers
861 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 ...
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. ...
42
votes
5answers
6k views

Burning ropes as timers

You have 2 identical ropes which burn at a specific rate, and an unlimited supply of matches. When you light one end of a rope, the fire will take exactly 1 hour to travel to the other end of the rope....
4
votes
2answers
790 views

What timezone am I?

It was 17:52 in the evening and I couldn’t wait for my class to finish. Only 8 more minutes… I really hate night school! I sat there pondering the stuff on the blackboard and wondering why he wrote ...
33
votes
16answers
12k views

Older twin's birthday is one day after younger's

I have been asked this puzzle in an interview. There was not a lot of time left so I couldn't solve it quickly and the interviewer kind of let it go as he had to wrap up the interview Foo and Bar ...
4
votes
2answers
250 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 ...
17
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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?
6
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7answers
19k views

A man is born in 1955

(I heard this in a movie and I think it’s pretty cool.) A man is born in 1955. Today, the 14th of August, 2017, he is 18. How is this possible?
1
vote
2answers
246 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 ...
3
votes
2answers
504 views

Your age and my age [closed]

This is not a very difficult problem, but it seems that it hasn't been asked here. It's one of my favorites, so here we go: I am twice as old as you were when I was as old as you are. When you ...
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 ...
-7
votes
5answers
358 views

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?
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
282 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
22
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 ...
7
votes
2answers
339 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 ...
11
votes
2answers
2k views

When was I born?

I was born just 10 minutes apart from my twin brother, but I celebrated my birthday 11 days after my twin brother every year. When was I born ?
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 $a.b \times \frac{a}{b} = 1$? ...
11
votes
2answers
485 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 ...
13
votes
3answers
910 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 ...
9
votes
2answers
495 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 ...
7
votes
1answer
258 views

What is it this Time?

Most clocks tell the time, but some are for letters. ...
11
votes
5answers
3k views

This puzzle is late!

I meant to release this puzzle 15¼ hours ago, and forgot again just over 9⅓ hours ago. But don't worry, it's fine. The puzzle is finally out. What is this puzzle about? NB: What timezone I am ...
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" ...
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 ...
3
votes
8answers
9k 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 ...
4
votes
3answers
584 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 ...