A thought provoking and I admit slightly unnerving blog post by Noah Sussman on the various aspects of time that we commonly take for granted, rightly or wrongly so. I know I'll be dealing with time a lot in future programming and as such I'm keen to sharpen my skills in the area. Now I know the areas where I could slip up, it's going to be interesting to see how I can rectify these potential problems. The blog post can be found here.
Update: And a link to a Stackoverflow post that discusses the various aspects you should consider when programming with regards to time (basically the 'answer' to all the issues we usually overlook) http://stackoverflow.com/questions/2532729/daylight-saving-time-and-timezone-best-practices