What is an intervention?
I want to tell you that yesterday I went to our Town Hall and swore allegiance to New Zealand.
I am now proud to be a Kiwi.
I took 4 friends to lunch beforehand. My sister sent me the money for the lunch. I know she would have liked to come but it would have been a waste of money to fly so far when she was here last October and she and her husband are coming to NZ on a cruise and (weather gods permitting) the ship will spend a day in Dunedin on April 11.
Congrats on your swearing in, Brian! You must be proud! I would be!
Regarding your question about what an intervention is, here in America when the family/friends of an alcoholic/drug addict have had enough of dealing with this behavior, they turn to an expert and hold an "intervention".
Basically, the sick family member is led to a room, and confronted by family and friends, and basically told that they are giving them the opportunity to go rehab. If they choose not to go, they will have to face the consequences of no more help from anyone until they deal with their problems.
So regarding the "ecard" that prompted your question, someone is telling their friends/family that if they are planning to hold an intervention for them, to wait until after St. Patrick's Day, which is a party day here in America, so they can have one last big party day.