(My question for the problem is very clear. If anyone can help I would appreciate.. Thank you...)
It may seem clear to you, but when you are asking for help the important thing is for the question to be clear to others.
The fact that you have no mentioned interrupts makes things even less clear. I can't imagine what is in your mind that makes you think interrupts may be part of the solution.
And this does not make sense "within the timestamp to store a sentence that I give (with the command) on the SD card.". How can anything be inside a timestamp - something can be stored along with a timestamp, but not inside it. I asked you in Reply #5 how the timestamp would be generated and used but you have not responded.
When you don't respond to questions it makes it very difficult to help. If you don't understand the question please say so.
Does the sequence of events in Reply #7 seem appropriate? I have been assuming all along that that is approximately what you have in mind.
What is preventing you from giving us a description of the overall project? If you had done that in your Original Post you would probably have a solution by now.