A lot of things did, in various places around the world. The events that jump out in my mind when those dates are mentioned are these:
May 14th, 1948:
The provisional government of the portion of the British Mandate for Palestine that was designated by the UN partition as reserved for Jewish administration declared that it was becoming a free and independent sovereign nation called Israel.
May 15th, 1948:
The massed armies of Syria, Egypt, Jordan, and Iraq rolled into Israel with big signs on the front of their tanks that read "Oh No You're Not !" .
