Photos appearing out of order
If photos appear out of order when they are first added, you can manually reorder them in Picasa by dragging and dropping them in the folder or album.
Incorrect sorting of photos is usually caused by an incorrect date in the EXIF data of the photo. EXIF data is photo information recorded directly to the photo file when the image is captured by your camera. Different cameras record different types and amounts of data, but virtually all digital cameras stamp time and date to your photos. A digital camera will start with a default date. If this date is not changed, an incorrect date may be applied to your photos.