provides attributes for normalization of elements that contain datable events to a custom dating system (i.e. other than the Gregorian used by W3 and ISO). supplies the value of a date or time in some standard form. Any string representing a valid date, time, or one of a variety of combinations.

The following are examples of custom date or time formats that are not valid ISO or W3C format normalizations, normalized to a different dating system

Alhazen died in Cairo on the 12th day of Jumada t-Tania, 430 AH .

The current world will end at the end of B'ak'tun 13.

The Battle of Meggidu (23rd year of the reign of Thutmose III).

Esidorus bix(i)t in p(ac)e annos LXX pl(u)s m(inu)s s(ub) d(ie) XI men(sis) O(cto)b(ris) ind(ictione) IIII

Not all custom date formulations will have Gregorian equivalents.

The when-custom attribute and other custom dating are not contrained to a datatype by the TEI, but individual projects are recommended to regularize and document their dating formats.

specifies the earliest possible date for the event in some custom standard form. A normalized form of temporal expression. specifies the latest possible date for the event in some custom standard form. A normalized form of temporal expression. indicates the starting point of the period in some standard form. A normalized form of temporal expression. indicates the ending point of the period in some standard form. A normalized form of temporal expression. supplies a pointer to some location defining a named point in time with reference to which the datable item is understood to have occurred supplies a pointer to a calendarDesc element or other means of interpreting the values of the custom dating attributes.