A Very Brief Guide To Why The Clocks Change
The general 'why' is that we make better use of our daylight hours.
The idea is that because we have more daylight during waking hours, we use less energy on lighting etc. Some argue this is offset by people doing more in the evenings (like driving around) and therefore there is no net gain. There are stats all over the place and you can probably find an stat to prove any point you like. On balance, most people seem to think that it does save some energy but not a lot.
This one is reasonably undisputed. People do more leisure and sport activities because there is more light.
Tricky. On one hand, more sunlight increases levels of Vitamin D (good), but also can increasingly cause skin cancer (bad). Health improves because people are generally happier when there's more light (sweeping comment we know and this isn't the place to expand on that). Health also improves because people can, generally, undertake more sport and other leisure activities. However, it depends what your leisure activity is and if it involves spending the evening in the pub then the Health arguments are a little thin. On balance, the opinion seems to be pro-health.
Again, fairly undisputed. Again, lots of stats available, mostly produced by people with an interest one way or another so you take your pick. However, the data tends to suggest an increase in general economic activity caused by people doing more due to longer daylight hours.
The Arguments Against Daylight Saving Time
Firstly, the simple hassle of changing your clocks, watches, computers and so on. It's a clear cut argument but is generally balanced by a 'how busy is your life if you can't spend five minutes twice a year adjusting your clocks'. Most people know the real hassle here is actually trying to find the instruction manual for your oven/DVD recorder so you can figure out _how_ to change the time. But that argument rarely features.
Secondly, Farmers and rural folk tend to dislike the change. There seems to be a general confidence that this is the case but fairly thin arguments as to why. One possibility is that there is a high proportion of Daily Mail readers among farmers and rural folk and therefore they dislike the clock change on the basis that any change is something to be upset about. (Apologies to readers outside the UK for whom the previous sentence will mean very little.)