I'm in love with these lists of "Falsehoods Programmers Believe About X." In case you haven't had pleasure, I've collected all the ones I know of here. If I missed any, let me know!

People's names do not change

People’s names have an order to them

My system will never have to deal with names from China

I can safely assume that this dictionary of bad words contains no people’s names in it

People have names

The time zone in which a program has to run will never change

The system clock will never be set to a time that is in the distant past or the far future

One minute on the system clock has exactly the same duration as one minute on any other clock

A time stamp of sufficient precision can safely be considered unique

The duration of one minute on the system clock would never be more than an hour

The local time offset (from UTC) will not change during office hours.

My software is only used internally/locally, so I don’t have to worry about timezones

I can easily maintain a timezone list myself

Time passes at the same speed on top of a mountain and at the bottom of a valley

Every day without DST changes is 86400 ( 60 * 60 * 24 ) seconds long

) seconds long If you have two UTC timestamps it is possible to calculate how many seconds will be between them even if one of the timestamps are a year into the future

The time 23:59:60 is always invalid

Places have only one official name

Place names follow the character rules of the language

Place names can be written with the exhaustive character set of a country

Places have only one official address

Street addresses contain street names

No buildings are numbered zero

A road will have a name

A single postcode will be larger than a single building

OK, but you don't get multiple postcodes per building

Addresses will have a reasonable number of characters — less than 100, say

All coordinates are in “Latitude/Longitude”

The shortest path between two points is a straight line

All programmers agree on the ordering of latitude and longitude pairs

Extra Credit:

Kevin Deldycke has made an even better version of this list, and hosted it on GitHub, where you can make pull requests to add new lists when you find them!