Curtin warrant: how the legal clock works
The 1988 Act says “...within seven days from the date of warrant”. Thus the date of the warrant is the first day. Apparently, the search took place on the eighth day, and so it was outside the time of the warrant.
The common law has no relevance here. It is the Interpretation Act 1937, Section 11 (h) which is relevant to the manner in which days are to be counted in Irish law.