On my computer, when I pull up a photo in Photoshop and rename the file before using "save as" the new name, the date and time of the photo become the time I did the "save as" for the file. If I subsequently pull up the photo, adjust it and just hit "save" it will assign a new date and time, though in the properties it will still show the date and time created, which shows the first time I did a "save as" to rename it from the camera's numeric name.
Obviously if one wanted to commit fraud one could just change the time on the camera. But life gets a little short for that.