You are generally considered tax resident in Ireland if you are present in Ireland for 183 days or more during a calendar year. Any part of a day generally counts as a day of presence. Ireland also has a separate 280-day test covering the current and previous tax years; add the Ireland Tax Residency — 280 Days / 2 Years rule to track that test.
https://www.revenue.ie/en/jobs-and-pensions/tax-residence/resident-for-tax-purposes.aspx