| Prolog term | Type | XSD string |
| date(Y,M,D) | xsd:date | YYYY-MM-DD |
| date_time(Y,M,D,H,Mi,S) | xsd:dateTime | YYYY-MM-DDTHH-MM-SS |
| date_time(Y,M,D,H,Mi,S,0) | xsd:dateTime | YYYY-MM-DDTHH-MM-SSZ |
| date_time(Y,M,D,H,Mi,S,TZ) | xsd:dateTime | YYYY-MM-DDTHH-MM-SS[+-]HH:MM |
| time(H,M,S) | xsd:time | HH:MM:SS |
| year_month(Y,M) | xsd:gYearMonth | YYYY-MM |
| month_day(M,D) | xsd:gMonthDay | MM-DD |
| D | xsd:gDay | DD |
| M | xsd:gMonth | MM |
| Y | xsd:gYear | YYYY |
For the Prolog term all variables denote integers except for
S, which represents seconds as either an integer or float.
The
TZ argument is the offset from UTC in seconds. The
Type is written as xsd:name, but is in fact the
full URI of the XSD data type, e.g., http://www.w3.org/2001/XMLSchema#date.
In the XSD string notation, the letters YMDHS denote digits. The
notation SS is either a two-digit integer or a decimal number with two
digits before the floating point, e.g. 05.3 to denote 5.3
seconds.
For most conversions, Type may be specified unbound and is
unified with the resulting type. For ambiguous conversions, Type
must be specified or an instantiation_error is raised. When converting
from Prolog to XSD serialization, D, M and Y are ambiguous. When
convertion from XSD serialization to Prolog, only DD and MM are
ambiguous. If
Type and String are both given and String
is a valid XSD date/time representation but not matching Type
a syntax error with the shape syntax_error(Type) is raised.
If DateTime and Type are both given and DateTime
does not satisfy
Type a domain_error of the shape
domain_error(xsd_time(Type), DateTime) is raised.
The domain of numerical values is verified and a corresponding
domain_error exception is raised if the domain is violated. There is no
test for the existence of a date and thus "2016-02-31",
although non-existing is accepted as valid.