I was on a trip to the middle east a year or so ago around mid spring.  I was offered what looked like a green plum.   The taste was very sour and hard (not soft like a plum). The locals called it "janarek" and for the life of me I can't find it here in North America.  The closest I've found were the yellow and golden plums  the mysterious green plums I'm talking about are a bit smaller and lot crunchier.   any ideas on what its name, and where I can buy it from? 
Maybe you had the Greengage plum.   