This could be some kind of Malware, but just the other day I was using Outlook and my calendar all of a sudden appeared in a foreign language. I didn't make any changes. I would like to know how this happened and how to fix it.
Ken if you didn't make changes then it is most likely some kind of malware. However I suspect one of the cats must have been walking around and happen to step on the keyboard causing the changes.
The names of the days and months as displayed in the Calendar is coming from the Language format settings in Windows and not from Outlook so you may have been in that area of the system and just clicked on the setting accidentally making the change.
This is easy to fix and when you change it back to your Vulcan language settings everything will be as you had previously set things.
To make the change simply go to the Control Panel, Select Change Date, Time, and number formats and then Select the appropriate Language under the Formats pull down. There are a number of additional language preferences settings that you may want to review but you most likely use the default settings.