Hello Masto
The htm files you have posted are of no use to us. What you have done there is to right-click copy App Inventor!
To post your project:
1) In App Inventor, select "Projects", Export selected project (.aia) to my computer. (you should be doing this frequently as a backup)
2) Attach the .aia file to your forum post as you did the htm files.
You can also post your blocks code - right click in the blocks viewer and select "Download Blocks as Image". That image can be inserted inline with your post text.
Hopefully, with that information, we will understand your question about dates - no idea what you mean at the moment.
Concerning building a database, there are a lot of options, so you need to be more specific and detailed about size/scale and the "specific place".