# The birthday puzzles

Here is a couple of birthday puzzles based some time in the future:

Puzzle 1

Your birthday was yesterday at exactly 12pm (noon). Today is 12pm the next day.
It is now 365 days till your next birthday.


How many hours until your next birthday from 12pm yesterday and why?

Puzzle 2

Your birthday was today at 11:59am.
It is now 364 days until your birthday.


What day this year is this describing and why? (Answer in dd/mm/yyyy format)

• Did my birthday begin or end at the times given? Are we talking about a birth instant? Or,,, are those considerations all part of the puzzle?
– humn
Jan 28 '16 at 21:52
• Am I using jewish calendar coz it has 364 days. Jan 29 '16 at 7:33
• @manshu The Hebrew calendar has 353-355 days, or 383-385 with Adar I (the leap month)...
– Will
Jan 29 '16 at 8:37

Puzzle 1 solution

From 12:00 noon on your birthday yesterday, it will be $366*24=8,784$ hours until your next birthday.

Why?

There's a leap year February 29 between this birthday and your next one, giving you an extra day between birthdays.

Puzzle 2 Solution

His/Her birthday is on

Any date. But there should not be any 29th February between those birthdays.

The Reason

If I celebrate my first birthday in Honolulu and next birthday in Kiritimati then I can say that I waited for 364 days for my second birthday because the difference in their time zones is 1 day.

Puzzle 1

8772 hours.

Reasoning:

There's a leap day before your next birthday, so it's 366 days. However, we're counting from noon, which means it's only 12 hours until the next day rather than 24.

Puzzle 2

07/11/2016

Reasoning:

You're located in Troll Station, Antarctica. By 11:59am, the clocks have already rolled back. You get the benefit of the roll forward (1 hour), but when it's your birthday again (00:00 on 07/11/2017) the clocks won't change until 02:00.
Normally at 11:59am it would be 364 days, 12 hours and 1 minute until your next birthday. However, because you're between clocks rolling back, you get 364 days, 11 hours and 1 minute, which we can round down to 364 days!

• The UK clocks change would work on any day from 25-31 October, 2020, since the change is 31/10/2021. That's not this year, though. Jan 29 '16 at 10:58