xs:date - an ISO 8601 date:
A prefix of the minus sign ('-') mean "BC" (before common era).
The common format is 'YYYY-MM-DD'.
You can add a time to indicate the "start of the day"--which looks just like the dateTime
A date instance is constrained just line xs:dateTime
xs:dateTime - an ISO 8601 date plus a time.
The date is separated from the time by a 'T': 2005-03-10T02:00:00-08:00
The time format is 'hh:mm:ss' with at optional fractional seconds and optional timezone offset.
The timezone is Greenwich Mean Time unless you specify the offset.
The constraining facets are: pattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive