| ## Text Encoding Initiative
### The XML Version of the TEI Guidelines # <when>

`<when>` | (when) indicates a point in time either relative to other elements in the same `<timeline>` tag, or absolutely.
Attributes | (In addition to global attributes)
`absolute` | supplies an absolute value for the time.
| Datatype: CDATA
| Values: Times may be given in standard form, as specified in the Encoding Declarations section of the header.
| Default: #IMPLIED
Note | Required for the element designated as the value of the `origin` attribute in the `<timeline>` tag.
`unit` | specifies the unit of time corresponding to the `interval` value.
| Datatype: CDATA
| Values: a semi-closed list of recognized time units such as ‘millisecond’, ‘second’, ‘minute’
| Default: %INHERITED;
`interval` | specifies the numeric portion of a time interval
| Datatype: CDATA
| Values: -1 or any positive number
| Default: %INHERITED;
Note | The value -1 indicates uncertainty about the interval.
`since` | identifies the reference point for determining the time of the current `<when>` element, which is obtained by adding the interval to the time of the reference point.
| Datatype: IDREF
| Values: Should point to another `<when>` element in the same `<timeline>`.
| Default: #IMPLIED
Note | If this attribute is omitted, and the `absolute` attribute is not specified, then the reference point is understood to be the origin of the enclosing `<timeline>` tag.

Example

    <when id="w3" interval="20" since="w2"/>

Note

On this element, the global `id` attribute must be supplied to specify an identifier for this point in time. The value used may be chosen freely provided that it is unique within the document and is a syntactically valid name. There is no requirement for values containing numbers to be in sequence.

Module Declared in file teilink2.dtd; Additional tag set for Linking and Segmentation: enabled by TEI.linking
Data Description empty
May occur within timeline
Declaration

    <!ELEMENT when %om.RO; EMPTY>
    <!ATTLIST when
          %a.global;
          absolute CDATA #IMPLIED
          unit CDATA %INHERITED;
          interval CDATA %INHERITED;
          since IDREF #IMPLIED>

See further 14.5.2 Placing Synchronous Events in Time

Up: 35 Elements