Yes, even today we can build something physical to remind us of God’s work. You could build something in your back yard, or in your home. Something that would have staying power and you would associate with whatever act of God you want to remember.
Write how the event happened, the date(s), and the circumstances around it. Write it by hand and keep it somewhere where you keep important documents or letters. Write it on your computer and put a shortcut on your desktop to remind you. Print it out and post it.
Post it & share it.
Post it on social media. Write it in a blog. Write it in a facebook note. Other believers want to rejoice and remember this event with you. Posting it saves, and also shares the info with others.
If it can be photo-documented, take the picture, frame it, and put it on your wall.
Put it on the calendar
Every year you transfer significant dates from one years calendar to the next. If there’s a specific date attached to an amazing work of God in your life, or that you have witnessed in the life of another, mark it down on the calendar. Transfer it from calendar to calendar every year. Commemorate it with your family.
Whatever it is, make sure it’s memorable and that it actually reminds you have what God did. What ideas do you have?