Few days ago I decided to help Yves with a datetime bug in Matukio (dating back to its "Seminar" roots). Everything seemed to be straight forward. I've worked with JDate in the past and had some experience with timezones. So I took the challenge thinking that I'll spend 2h and everything would be fine. Well, as it often happens a 2h job turned to be a one and a half day job... (this could make a very good blog post about estimates, but I'll do that another time...)

Let us examine the problem at hand. User A fills out a form, which has a field that stores a date. The best thing to do when you store the date in the db is to convert it to UTC. Why to UTC? Well this way you can have always a starting point and when you present the output to the user you can add different timezones depending on the users position. The trick here is to convert the date back to UTC. Fortunately JDate can help us with that. If you look at the JDate class in libraries/joomla/utilities/date.php you will see that the constructor actually expects 2 parameters -> the date and the timezone. So when you save a date you would generally want to do something like this: