Unlike the TARDIS from your beloved Doctor Who, the TARDIS teapot can not, unfortunately, transport you to any point in time-space.
The TARDIS teapot can, on the other hand, transport you to a time and place where you have a lovely pot of tea in front of you, ready to be consumed and meet your caffeine intake requirements for the day.
Of course, if you don’t care for tea then it’s probably best to think of this as more of a pitcher than a teapot. It’s not as if any wibbly-wobbly-teamey-wimey things would occur were you to place any other liquids suitable for human consumption within the container.
Speaking of “within,” it’s perhaps best to specify that the inner dimensions of the tea pot do not defy the laws of physics and are only as large as they appear, which is a rather large 750ml.