Mix your vinegar, sugar, water, prepared mustard, salt, celery seed, mustard seed and cloves in a large saucepan. Let it boil and then lower the heat so that it simmers for about 10 minutes. Remove from the stove and allow the mixture to cool. Get a large, glass jar with a lid, and put your eggs and onions inside. Pour in the vinegar mixture until the eggs are completely covered. Close the jar, and place it in the refrigerator to chill overnight (or at least for 8 hours). These will last in the refrigerator for a week.