If your photos do not have date stamps, simply log-in to your account and go to the day that you want to post to (using the date entry fields above the calendar or by clicking the calendar itself), and then click “Add to This Day” to upload directly to that day. When you take this route, Eachday trusts you to know the dates of your memories.
Some Eachdayers edit, color correct, monkey with and re-save all of their photos before uploading (thus often removing the date stamp), so this is the primary method they use to upload. The only difference is that you need to remember the date the memory was captured. That’s simple enough!