I've been looking for this tv show for a while, but I can't find any references to it at all. I know it is definitely pre 2001
The series starts with some teen from the future looking for someone who looks like him who is from the past, and find someone in the 90s (I think it's the 90s).
He communicates with him and they agree to trade places, but as time travel is illegal, they have to keep the switch secret. Most of the series is then about each of them adapting to their unfamiliar environment and situations (future birthday party, past romantic dates), while remaining in contact with each other.
The guy from the present asks the computer to "appear" as a person, which he does in the first episode for the rest of the series. I think the actor might be a comedian.
I remember that the guy from the future had a "watch" which allowed him to teleport and a few other things, but one episode it ran out of power and he ended up using a washing machine to create a green goo which was the power source.
On the future side, because the person who had switched was extremely healthy (played football (soccer) regularly), he beat his "rival" in a future competitor sport.
It finished off with them trading places again just in time as the future police were investigating allegations of time travel, but the series ended with the person from the present entering a code on the time travel belt to send it back to the future, but didn't take it off first and disappeared.
There was a second series, but I don't know anything about it other than it existed.
I think I watched it on UK CITV, but that doesn't give much indicator where it's from. I think it was set in the UK though.