2 pounds carrots, cut lengthwise into 1/4-in. thick strips
1-1/2 cups sugar
1-1/2 cups water
1-1/2 cups cider vinegar
1/4 cup mustard seed
3 cinnamon sticks (3 inches)
3 whole cloves
Place carrots in a large saucepan; add enough water to cover. Bring to a boil. Cook, covered, until crisp-tender, 3-5 minutes. Drain. Transfer to a large bowl. In another large saucepan, combine remaining ingredients. Bring to a boil. Reduce heat; simmer, uncovered, for 20 minutes. Refrigerate, covered, overnight to allow flavors to blend.
Transfer mixture to jars. Cover and refrigerate up to 1 month.