You’ve invented a time machine, but due to a weird quirk of the physics involved, once it’s activated, it will only be able to travel in one direction - further into the past, or further into the future. There is no possibility of return to the present time (well, unless you visit the past, then wait).
The device is the size of an ordinary telephone kiosk - enough room for one, maybe two adults and a few belongings - the inside of the machine is a bit smaller than the outside - items placed inside the device will be unaffected by the travel through time (so you won’t age faster than normal if you go forward, and you won’t revert to a blastocyst if you go back).
Also, it’s a clever machine - it binds itself to the nearest large gravity well, and will not rematerialise in an immediately dangerous situation, such as an active volcano, the surface of what is now an ocean, under a mountain, or directly in front of a dinosaur, and you won’t jump back six months and find that the Earth isn’t here anymore. You’ll reappear in a fairly safe location as near to the geographical point from which you departed. (this might cause problems with travel back to when the earth was a molten ball, but let’s not get too complicated right now)
So your options consist of:
-Travel once or continually into the past in hops of any timespan you like, as many times as you like, until you’ve had enough and you stop.
-Travel once or continually into the future in hops of any timespan you like, as many times as you like, until you’ve had enough and you stop, or you reach the point where the universe explodes or something.
-Do nothing - stay at home, optionally sell the machine to someone braver than yourself.