Someone here mentioned that the #555timer was designed 55 years ago https://en.wikipedia.org/wiki/555_timer_IC So I guess that makes 5/5 #555timerday!

#TinkerCAD .com can simulate this quite nicely - No real breadboard required.

Its 555 Tmer day! The 555 timer is 55 years old! #555Timer #555TimerDay

https://www.ti.com/lit/ds/symlink/lm555.pdf?ts=1777974716675&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fen-us%252Fdocs%252Funiversalsearch.tsp%253FlangPref%253Den-US%2526nr%253D1668%2526searchTerm%253D555+timer