Not even just on this forum but also in my day to day life I have heard people asking if it is wierd that they are dating someone drastically older/younger than themselves. My friends and I came up with a formula to act as a guide. Obviously, there is no accounting for love and there are exceptions to every rule but this helps those I talk to.
The Standard Creepiness Factor
(Age/2)+7=Youngest person you can date without being a creeper.
For example: I just turned 30 so half my age is 15. Add 7 and you come to 22. I should really be looking for someone 22 or older.
If I was 40 half my age is 20, add 7 and the youngest person I can date without being a creeper is 27.
Again, this is not the "end all, be all" formula. Someone could look/act/feel/etc. either younger or older than they actually are so there are definate gray areas. Just remember that if you love someone and they love you back you have something special. Don't get too hung up on details, remember that age is just a number.
Hope this helps.