There was no set way of spelling so "dide" isn't significant. "Monoment" is spelled monument now.
The big letters IHS at the top centre is a Christogram, a monogram symbolising Jesus Christ, an abbreviation of Jesus in Greek.
Is it original or a replacement/copy? It seems very well-preserved.
I think it says February 12th 39/40 which would probably be 1539/1540. There was a change between Gregorian and Julien calendars around 1552 I believe, but not sure about this, and others may correct me.
Regards.
The calendar changed from Julian to Gregorian in many countries on the continent of Europe in 1582. They were mainly Catholic countries as the change was led by King Philip of Spain, a Catholic monarch who ruled several European countries, and the Pope.
The Gregorian calendar was adopted by Catholic clergy in some places in Ireland but not by the Church of Ireland. That resulted in anomalies such as the date of a person's burial being recorded days before the date of death, or a will dated after a death date. Ireland officially changed to the Gregorian calendar in1752, the same time as England.
Scotland adopted the Gregorian calendar in 1600.
Year on the monument looks to me more like 1739/40 than 1539/40. If it was 1539/40 it's not an original inscription. It may not be original if the year is 1739/40.
Where is it?