March 17 is more often a day I remember because it was my paternal grandmother's birthday than because of St. Patrick's Day. I remember her fondly on this day and regret that I was in Japan during the later years of her life. I guess that it's hard to get into the holiday itself when it frequently involves alcohol consumption and you don't drink alcohol.
St. Patrick's Day is one of those secular holidays (yes, I know it was originally a religious holiday) that Japan hasn't absorbed for commercial purposes yet. Some Irish and British pubs in Tokyo have parties at this time but most Japanese people know little about it.
Interestingly though, the idea that 4-leaf clovers are lucky is something at least a few of my students believe in. This is curious because the number 4 is considered unlucky in Japan because it can be pronounced as "shi" which also means death. This is similar to the situation in western countries where many hotels do not have 13th floors. In Japan, there is often no room 4, seat 4, parking space 4, etc. So, one must wonder how 4-leaf clovers came to be considered lucky where there is almost no Irish cultural influence to make clovers a part of the cultural mythos.
To all those who celebrate this day, Happy St. Patrick's Day. And, Happy Birthday, Grandma. I miss you.