Final answer:
The minimum ageing period for XO Cognac is 10 years in a barrel, following a regulation update on April 1, 2018, to reflect its premium status.
Step-by-step explanation:
The minimum ageing period in a barrel for XO (Extra Old) Cognac is 10 years. This regulation was updated as of April 1, 2018. Prior to this date, the minimum ageing requirement for XO Cognac was 6 years. However, to ensure a higher quality product that reflects the prestigious classification of 'XO,' authorities increased the ageing requirement to 10 years. This change aligns with the premium nature associated with XO Cognac, delivering a more matured and nuanced flavor to consumers.