The Leaving Cert will be extended from next year, with two extra days being added to the timetable.
Education Minister Joe McHugh announced the change today, with the aim of reducing pressure on students and avoiding exam clashes.
It means there'll now be 15 days of exams in total - with the schedule running into a fourth week.
Core subjects such as English, Irish and Maths are not impacted by the schedule revisions.
Speaking in Dublin today, Minister McHugh said: "I am confident that the small number of students who may have to sit three examinations in a single day will be significantly reduced as a result of these changes.
"The change is about trying to ease pressure. From talking to Leaving Cert students I hear how the exams play on their minds and any changes that we can make to ease that are really welcome."
The State Examinations Commission does acknowledge that it's still possible some students will have to sit three exams in a single day given the "wide subject choices" available to students.
No exam is scheduled for the afternoon of the 15th day of the exams next year, with education officials saying the space will instead be used from 2020 for new exam subjects.
Next year's Leaving Cert exams will begin on June 5th, and the full timetable has been published online today.