Does Outlook Express have a Calendar?
In a word, no.
And unfortunately, it gets even a little worse than that.
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There’s not even an add-on to perform the function that I’m aware of. As I discussed “How do Outlook and Outlook Express
Relate?“, Outlook Express wasn’t really designed to support add-ons, calendar or otherwise. If you don’t like Outlook (which does have a calendar, and much more), my recommendation is to find a separate, stand-alone calendaring or personal information management package to run in addition to Outlook Express.