Times when only small letters will do (5)

'times' is the definition.
The definition and answer can be both related to time as well as being plural nouns.
Perhaps there's a link between them I don't understand?

'only small letters will do' is the wordplay.
I cannot quite see how this works, but
'small' could be 'wee' (Scottish term for small) and 'wee' is present in the answer.
This may be the basis of the clue (or it may be nonsense).

'when' acts as a link.

Can you help me to learn more?