This is the relevant information: This has been achieved 39 times in total, for the first time by Wales in 1908, and most recently by Ireland in 2018.
This justifies what answer for what question? Q & A:
Passage: In rugby union, a Grand Slam (Irish: Caithreim Mhor. Welsh: Y Gamp Lawn. French: Grand Chelem) occurs when one team in the Six Nations Championship (or its Five Nations predecessor) manages to beat all the others during one year's competition. This has been achieved 39 times in total, for the first time by Wales in 1908, and most recently by Ireland in 2018. The team to have won the most Grand Slams is England with 13.

Question: Based on this passage, when did ireland win the grand slam last?
2018