As the anonymous reader discovered, however, there is a solution--one that's less obvious than it might appear at first. The iPhone will honor whichever sorting option you select . To change the sorting order there, launch iPhoto, select Events, and then choose View -> Sort Events. You can then sort Events by date (in chronological or reverse-chronological order), alphabetically by name, or in a manual order of your own creation.
But, wait, there's more: If you switched to iTunes now, your photos still wouldn't be in the order you wanted; they'd be out of order on your phone, too. You must first quit and relaunch iPhoto. Once you've done so, iTunes will notice the new sort order you've set for your Events. When you sync your iPhone this time, events will appear the way you want them to.