Think like an OO programming language. First you select the namespace, then the class, then the member. Think of the internet, first you select WWW, then the site, then the top level domain. I argue that the correct date format should be year.month.day.hour.minute.second. Think about naming your directories by date, for instance, you want to sort all of the picture you took of your girlfriend from your cell phone. If you were to name the directories by month, day, year, you would group all of the March's together and when you open the picture of your girlfriend you could inadvertently open the image of your girlfriend last year... good luck explaining that one. BUT if you were to name the directories by year, month, day, then you'd be able to get more pictures :D