Hi,
There is no real localization, but HE reads encoding names from system settings, so they are displayed in system language (not local).
To create date/time insert templates, also system function are used. But they display texts not in system language but in local (ones selected by user in Control Panel -> Regional and Language Options -> Standard and Formats). You can check this by hovering clock in system tray. The language used there should be also used when inserting date time in HippoEDIT. Is this does not match on your machine and what you have selected in Standards and Formats ?
Best regards,
Alex.