Only in Israel: Why the milk was sour

This morning, one of my daughters went to the makolet (small grocery store) to buy milk. Normally, we only get 1% fat (the lowest there is in much of Israel) milk in this house, but this morning she came home with three 1% bags and two 3% bags. I poured myself a cup of coffee and added some 1% milk. It was sour.

I took it back to the makolet and the owner told me to go take two more bags (I