Automatic date field bug ?

I use MailPoet V3 for sending a weekly newsletter for my photoclub. Each week the newest post are send to ours members.

I discovered the use of automatic date fields (year, month, day, day of the wwek), it is a great feature, that reduce the work need to administer the newsletter, but the date is updated on sent newsletters too!

If you visit tha link I indicated you and click on the “21 avril 2018 Du nouveau sur clubpm.qc.ca édition du samedi” you will view the conctent of our last newsletter, but the date indicated on the web page is the today date, not the sent date .

How to indicate to the page to keep the sent date ?

The page I need help with: [log in to see the link]