Realizing that most of the TV shows I watched as a kid are now over 15 years old like Mighty Max, Swat Kats, Pepper Ann, and Recess.
Realizing that the classmates I went to high school with are now married and have kids of their own.
Recognizing more than 75 percent of the 80's-90's references present in Regular Show.
Realizing that children born in the 2000's are now teenagers in high school.
Realizing that the SNES, Sega Genesis, and GBA are over 20 years old now.
Overhead projector, VCR, typewriter, Classic Apple Macintosh, rotary phones, Laser Disc - Name me one child or high school teen from the current generation that has even heard of or used one of these to watch movies, play games, communicate with each other, or solve word and math problems.
Bulky TVs were prevalent back in the 80's and 90's.