Sometime / Sometimes

[jack]

Are these correct? What do these mean?
1. You can drop by sometimes.
2. You can drop by sometime.

If #1 is incorrect, why is #3 correct?
3. You can drop by ocasionally.

 

[Mister Micawber]

'Sometime' means at an unspecified future time.
'Sometimes' means occasionally.

Both sentences are correct, but carry different meanings.