This tardis uses a combination of command blocks and redstone. You press the button to open the door of the tardis then walk forward into the tardis and you will get tped inside. Sit in the chair (aka minecart) and press the button. It will take you forward in time. To stop time traveling, press the button again. To exit the tardis, turn around and step on the pressure plate to walk out. By the way when you "enter" the tardis, you get tped to somewhere underground. The minecraft version this is for is 1.16.4.

I will continue to update this through the next couple of months.