The code does work, but I did it on enter, not initialize. I've done it because it shouldn't be visible when the document is open. Also it allows me to type my own time. Thanks!

@Mayank_Gandhi it's pdf. 

Hi again, I found the solution. It wasn't about the acrobat reader. Actually the data binding was set in a wrong way (no data). I took the solution from this topic: https://experienceleaguecommunities.adobe.com/t5/adobe-livecycle-questions/subform-instances-are-not-retained-after-saving/td-p/330219 ...

Thanks! I'll take a look and let you know.

unfortunately I can't share it.