riddle in the spirit of Feb. 29


Twins Molly and Polly were born at 1:02 AM and 1:58 AM respectively on November 1, 2009. Who was born first?


The first was born at 1:58am. Two minutes later the clock was turned back at the end of Daylight Savings Time. Two minutes after that, the second child was born.


Well, that didn't take long, and it isn't even Feb. 29 yet!

I've always been intrigued by the switchover to/from daylight savings time. When you "spring forward", the time 2:30 AM doesn't exist, and when you "fall back", 1:30 AM happens twice in the same day. I've always thought that an enterprising crook could rob a store (that is open at that hour) and have an ironclad alibi.


The other way around here :-)

- Pauli


Or otherwise if the twins were born in the UK, where clocks had changed a few days earlier that year (on October 25th).


In Europe, DST switches back to standard time on the last Sunday in October, not early November. So it was a U.S. domestic riddle.


It used to be the same in the US, but they changed it a few years ago.



So it was a U.S. domestic riddle.

Actually, that could just as easily have been Greenland, Saint Pierre & Miquelon (an interesting twist of history off Canada's east coast in the Gulf of Saint Lawrence retained by France through the Treaty of Paris in 1763), Canada, many islands in the Caribbean, etc.

The DST switch on that date is far more widespread than simply the U.S.

Oddly, the riddle's location could not have been in Hawaii, much of Arizona, or several other U.S territories since they do not observe DST. Also Canada's prairie province of Saskatchewan does not subscribe to DST either. Probably a few other holdouts as well...


Actually, that could just as easily have been Greenland, Saint Pierre & Miquelon .... Canada, many islands in the Caribbean, etc.

My understanding of this is that all these countries deliberately key off of the US time zone rules and residents of these locals are often upset that we (the US congress that is) essentially force them to make these changes.

I for one wish we'd just set our clocks based on DST all the time, It's only 1/3 of the year that we're off of DST now anyway.


I guess its only fair that, as a Canadian invented time zones, the Americans push back a little bit here and there. Keeps them in the game...

After all, much of the world succumbed to the idea of the New Zealander who originally wanted more daylight to collect his insects.

As for being forced to make changes, Saskatchewan and Arizona seem to be doing just fine resisting the urge altogether.

However, in the words of a late prime minister of ours: "Living next to you [the U.S.] is in some ways like sleeping with an elephant. No matter how friendly and even-tempered is the beast, one is affected by every twitch and grunt."

Being a morning person, I tend to agree with you about staying on DST all the time.


As for being forced to make changes, Saskatchewan and Arizona seem to be doing just fine resisting the urge altogether.

China too. China as a whole only has one zone that spans five.

U.S. domestic riddle.

Sans Arizona.


Except the Navajo reservation!


Hence "much of Arizona"... :-)


Is the Navajo reservation considered a subset of Arizona? Just curious how a sovereign nation surrounded by another is considered.


Is the Navajo reservation considered a subset of Arizona?

Probably depends on who you ask (and even when)! As far as I know, for example, their cars all have Arizona-issue license plates.

To some extent, the reservations (there are at least 5 different tribal reservations that I can think of immediately, and surely several more, in Arizona) are self-governing. But, they are subject to various US laws as well.


We had an intern at work who was asked to write a function to switch into and out of DST. I was asked to review the code. (There were issues with documentation, variables declared that had long been deleted from the code, and so on. But this isn't about that.)

The intern followed the current U.S. rules. I reminded the intern that we (who will remain nameless) are a global company. We went to Wikipedia and checked out the article on daylight saving time (summer time). Not that it would need to be spot-on accurate -- it would give us a flavo(u)r for the variety of rules used around the world so we could give the code the right configurability. The rules, of course, are set by governments (not tech people) -- then they must be dealt with by programmers.

The code was reworked to deal with all the variations we found in the wiki, including:

* No change (tropical countries).

* Move forward in the early part of the year (northern hemisphere) or in the latter part of the year (southern hemisphere).

* Move at local time (U.S.) or at a fixed UTC (EU).

* Move on the first, second, third, fourth or last (whatever day of the week) of (whatever month).

* Move on the (whatever day of the week) BEFORE the 1st, ..., last (whatever...) (Russia, I think).

* Move on a fixed date (Israel, I think....).

* Move any number of minutes (Newfoundland moved 120 minutes one year instead of 60. At least I think it was the Newfies....).

* A couple other variants I can't remember without digging up my list.

And finally, the function must set a flag during the overlap (two 1:30 a.m.'s), and set a flag when the skip forward occurs (no 2:30 a.m.).

The second rev of the code was VASTLY improved. GOOD intern! :-)

Key takeaway: DST rules are established by (and changed at the whim of) governments. YMMV. Greatly.

I believe WinXP has a database file of DST rules for the Windows Time Service to use. (The timezone database feeds the pulldown in the clock config window.) When governments change DST, MS has to push a new database (via Windows Update). At least I think that's how it works. There was a KBxxxxxx item we had to make sure to apply before the end of October the year the U.S. changed from last Sunday in October to first Sunday in November. Not everybody did the update....



The reality of timezones and daylight savings time is a complete mess. The zoneinfo datebase does a pretty good job of keeping up to date and reading through the database is quite enlightening as to how stupid and mindlessly fiddly governments can be. Got to be seen to be doing something -- I know lets change the time zone stuff again, that will get us noticed.

February the 30th? Yes. Quarter hour time zones? Naturally.

- Pauli


Hi Don,

Nice riddle. I had read a similar one some years ago, but had forgotten about it.

Back to Leap Year, apparanty Microsoft doesn't have a full understanding of it:

Microsoft blames Azure cloud computing outage on leap year

Very funny - unless you were affected.



Good grief, blaming it on leap year? It's not like we haven't seen at least a dozen of these since software was invented!

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