If I understand, you took all of the Glance Of The Day photos for all days at the same time...maybe on day 7. You want to change the date of your Glance Of The Day photos so that it seems like the day 1 Glance Of The Day photos were actually taken on day 1 and can then be organized with other pictures from day 1. If that's correct, there's not a simple way to do that in Windows, but there are a few options. I'm assuming that you're using Windows but if not, there may be similar options for MacOS. I'm not a Mac guy.
Option 1 is to download 3rd party software that can edit the properties of a Windows file. Using the 3rd party software, you would change the "date created" value of your picture files.
If you don't want to use 3rd party software, option 2 is to do something similar in Windows but you will need to sort differently. In Windows, open File Explorer and right-click on one of the files that you want to re-date. Click on Properties. In the dialog box that opens, click on the Details tab at the top. A few rows down, you'll see Date Taken. You can click on the date value shown there and change it. You can either type in a new date or click on the little calendar icon and pick a date from the calendar.
The issue with this approach is that Windows files have several different date related properties. Date taken is not the same as date created or date modified (or date acquired, or date last saved...etc.). The date created and date modified values will stay the same. You would then need to sort your photos based on the date taken value, which requires a few extra steps. In File Explorer, select Details from the Views drop down at the top. This will typically give you a list of the files with information on the file name, size, type, and date created/date modified. Right click on an empty area to the right of the column titles in this view and you'll see a list of properties that you can display, with a check next to the properties that are currently being shown. Click on More at the bottom of the list and you'll see dozens and dozens of file properties that you can show. Scroll down to Date Taken and click on it. Date Taken will now be listed and you can sort on Date Taken to keep your Glance of the Day photos with your other photos from the same day. This isn't quite as complicated as it sounds, but it's not simple either.
Option 3 is to rename your photo files. Put something like "Day 1-" at the beginning of all day 1 photos, including your Glance of the Day photos. You then sort based on Name and your photos should be grouped correctly. Since picture files are usually numbered sequentially, photos from the same day will still be listed within that day in the order that they were taken. This isn't hard but can be a lot of work, depending on how many pictures you have. There are also 3rd party software programs that can do this in bulk, i.e. pick all photos from day 1 (including the Glance of the Day) and put "Day 1-" in front of all of them.
Sorry I can't think of anything easier.
Edit - Looks like Mark and I replied at the same time. Between his Apple answer and my Windows answer, hopefully we have you covered.