I followed up a suggestion on another blog (EKF) and tried using Google calendar. I see its attractions, but I don't think I'll be using it regularly. The main reason for this is that I commute quite a distance into work, and often use this time for planning: in the morning, to preview my timetable for the day, prioritise tasks etc.; in the evening to review how things have gone and decide what I need to pack for the next day.
These simple tasks can easily be done using an old-fashioned paper diary and notebook; and it would actually be quite hard to do them electronically, since I don't have reliable access to the Net while I'm travelling. Keeping more than one diary leads inevitably to ambiguity and confusion (as I've found in the past when I tried to use a hard-copy diary alongside the calendar on my PDA). So Google calendar, I suspect, is not for me.
Conclusion: electronic tools can be marvellous and really improve your life, but you need to be sure they truly fit your needs. In some cases, the old-style technology can still be more efficient.
Two Years Later...
11 months ago