It may have to do with the localization defaults - e.g. it might be set to US English and iso_1. If you connect using utf8, you might see the full datetime....
....note that it isn't the server truncating the date - it is the client API layer - hence the localization aspects. Same is true using MONEY datatypes - with a US default localization, it "seems" to truncate at 2 digits and defaults with comma's as thousands separators.....however, if you use a different localization, you see all 4 digits of precision.