Key legal question
When did the one-year limitation period for the tenant's unjust enrichment claim begin to run?
Extracted holding
It did not begin upon service of the disputed utility invoices; it begins only when the claimant actually learns the true legal situation and thereby gains sufficient knowledge of the unjust enrichment claim.
Extracted reasoning
For Art. 67 OR, actual knowledge is required. Mere awareness of the invoice and the possibility of inquiry is insufficient. The appellate court wrongly relied on a duty to inform oneself rather than on the claimant's actual knowledge.