But if you have no electricity, that’s not a good food source.
Yaaa... I was making a joke about the longevity of foodstuffs and the some-time silliness of sell-by dates.
Still, it is amazing how long a cup of plain joghurt will last under refrigeration. Most people might dump it after a week or two. Months or years after it is still consumable though.
Trust your nose, not the government.