I wish to change the hour format in Calendar to a 24 hour format. Can this be done? How?
Go to System Preferences...>Language & Text>Region>Times>Customize..., and remove AM/PM from the Short/Medium/Long/Full fields.
In case the solution is still elusive:
as Ferd II suggested, go to Language&Text > Region > Times > Customize
now use the drop down menu to change each hour element to "0-23" or "1-24". Removing AM/PM won't help.
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