When to commemorate the Easter Rising (approximately)?

I believe the answer is:

ascensionday

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'commemorate the easter rising approximately?' is the definition.
I can't tell whether this defines the answer.

'when' is the wordplay.
I cannot quite see how this works, but
'when' could be 'on' (I've seen this in other clues) and 'on' is present in the answer.
This may be the basis of clue (or it may be nonsense).

'to' acts as a link.

Can you help me to learn more?

I've seen this clue in The Daily Mail.

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