Ever save a document only to suddenly realize that you just overwrote something you meant to keep? Have you ever opened a folder only to discover that what you thought was in there was no longer there? Have you ever installed a utility that somehow wiped out almost everything? Have you ever decided to do some routine housekeeping in your computer’s address book or old e-mails only to find out days later that you inadvertently wiped out the address or confirmation e-mail of your biggest client? You get the idea.

If you have ever lost something, have had your hard drive crash or just deleted something that you wish you hadn’t deleted, you’ve also probably wished you had a time machine to take you back in time to reclaim what was lost and bring it back with you into the present. Well with Apple’s upcoming Time Machine, that’s exactly what you’ll be able to do.

At the recent World Wide Developer’s Conference (WWDC) in San Francisco, the attending audience was first to get a glimpse of the upcoming release of Leopard, Apple’s next iteration (10.5) of its OS X operating system. Only some of the many new features were demonstrated but the one that got my attention was Time Machine. Built in as part of the OS itself, Time Machine is technically a backup, but to call it a backup utility would be quite the understatement.

To introduce why Apple decided to create Time Machine, they began the demo by showing a survey of its users in which they found that only 26 percent backup their computers. But even that alarmingly small number only backed up sporadically at best. Of that 26 percent, they found out that only a puny 4 percent performed a regular, automatic backup of everything.

While those numbers are probably different for Windows users, most everyone knows regular backups should be made, yet most of us just don’t bother to do it. Of course, when the inevitable crash occurs, there’s the typical wailing and gnashing of teeth followed with the lament that they knew better and should have backed up. The reason most of us don’t do it is because it’s either too complicated or we just don’t want to deal with the hassle. Time Machine takes care of all of those objections and does so in a new and elegant manner. In fact, I’d chance to say that using Time Machine might actually be fun.

So here’s how Time Machine works. Just connect another hard drive to your Mac. Leopard will detect the new drive and ask if you want to use it for Time Machine. Doing so dedicates the drive to that purpose. You can also use Time Machine with a server if you like. The first thing it does is back up everything. All of your files, applications, utilities, even the OS itself gets backed up. After that, anything you do on any hard drive gets recorded to the Time Machine drive. So basically, you hook up a hard drive, say “yes” and go about your business. Leopard does everything for you, which is why I believe most every Mac user will use this. Time Machine is EASY and non-invasive.

So when the disaster eventually does strike, that’s when Time Machine does its truly amazing stuff. Let’s say you open a Finder window and discover a file is missing. No problem. Keeping the window open, you click on the Time Machine icon in the Dock. The window moves towards the center of the screen and the entire desktop behind it visibly slides down and out of sight.

What you now see is your open window suspended in outer space complete with an animated field of moving stars. Behind the open window are multiple iterations of that open window stretching back towards a distant galaxy into what seems an infinite point in space. To the right is a translucent vertical time line that expands as you move the mouse pointer over it. Clicking in any point on the line moves you back through previous windows by flipping through them and bringing the corresponding window to the front.

Each open window displays its contents as it appeared at that date and time. You can manually continue to move back until you come upon the window that displays your missing file. Or just click on the dimensional back arrow and Time Machine will automatically whisk back through time and the windows until it finds something that changed. The animation stops and you see the open window and everything that was in it at that date and time. It’s a fun animation to watch as the open windows keep flipping towards you.

Before you bring the file back into the present, you can double click on the file and it will run so as to confirm that this is truly the file you want. To bring it back to the present, just click on the Restore button. The star field disappears, returning you to the normal desktop but now with the Window containing the missing file. It couldn’t be simpler.

Time Machine works from within applications as well. For example, if you deleted a record in Address Book, it will show it’s not there when you search for it in the Address Book window. Leave it open, click Time Machine and perform the same operations with the open Address Book application window. You go back until the missing record appears, click Restore and the record is brought back into the current Address Book application window.

Apple has a demonstration of Time Machine up on their Web site for you to see. Just go to the Sneak Peek of Leopard and watch the QuickTime video of Time Machine. You can also see it in action watching the WWDC keynote video.

I can almost promise you that if you have never backed up before, you will now. That’s because in Time Machine, Apple has removed virtually all of the objections we’ve used to excuse ourselves from doing it. Just hook up a drive and forget about it. It’s a completely thorough, transparent, automatic backup that’s fun to use when we need something we’ve lost.

I find myself almost hoping I’m going to lose something just so I can use Time Machine. Just this one feature will make me want to upgrade and it’s only one of well over a hundred new additions to OS X 10.5. As far as I’m concerned, Leopard can’t get here quickly enough.