Is a 17 year old able to date a 25 year old?

It is legal, but sometimes the two might not get on. For example, the 17 year old is likely to still have commitments with school which the 21 year old might not like. Equally, 21 is old enough to drink, but 17 is still below the age of consent in some countries, so the 17 year old might not be able to go out with the 21 year old to many places.