Plural of 'Word of the day'?

Each day in the office we choose a 'word of the day.' We have started to keep a list of the words.

What should the list be called?
1. Words of the Day — implies many words but one day
2. Word of the Days
3. Words of the Days

Solution 1:

The plural is indeed Words of the Day. Nouns are pluralised, and the adjectival phrase of the Day is not.

There are other examples one might cite: President of Zaire; Queen of England — referring to more than one president or queen requires Presidents of Zaire, Queens of England. In some cases (for example between 1952 and 2002) there has indeed been more than one Queen of England at once, but Queens of England is still the title for a list.