Contemporary,
What you have in your contract may not be enforcable. The rules of the PRTB have precedence over anything you may have agreed with your tenant in a contract.
You can get details at prtb.ie, I have extracted the notice periods required below, but you should check the PRTB website as you can only terminate your tenacy under certain conditions. If your tenant has been in your property for less than 6 months then you should be alright with 28 days notice, but after 6 months the tenant gains rights which allow them to stay for an extended period.
You should really have a good read of the information on the PRTB website.
Notice Period Duration of Tenancy
28 days Less than 6 months
35 days 6 months or more but less than 1 year
42 days 1 year or more but less than 2 years
56 days 2 years or more but less than 3 years
84 days 3 years or more but less than 4 years
112 days 4 or more years