HTML and CSS Reference
The contents of date construct elements should be declared according to the date-time format defined in RFC 3339 .
Date and time should be separated by an uppercase T , while an uppercase Z should be used when the numeric time zone
offset is omitted (Listing 8-35).
Listing 8-35. Some Valid Timestamps in Atom
All date values of Atom new feeds should comply with the ISO standard on date and time representation (ISO
8601:2004 ) and the W3C date and time format  specifications, as well as the ISO 8601 Conventions in the W3C
Recommendation “XML Schema Part 2: Datatypes Second Edition” .
There are three container elements in Atom:
feed element, which contains the entire feed
entry element, which contains a simple news entry
content element, which contains a full story (the content of a news entry)
The next sections describe these containers in detail.
The feed Element
As mentioned earlier, the top-level element of Atom feeds is feed ; it contains the news feed metadata and contents
(all other Atom elements). One or more author elements are required for feed elements, except all child entry
elements of the feed element contain at least one author element. Exactly one id element must be provided for all
feed elements. The feed elements must contain exactly one updated element. Exactly one title element is required
for all feed elements. The feed elements should contain one link element with a rel attribute value set to self .
An arbitrary number of category and contributor elements can be included in feed elements. Only one
generator is allowed for each feed . The same holds for icon and logo elements as well.
The feed elements can contain a maximum of one link element with a rel attribute value set to alternate that
has the same type and hreflang attribute values. Beyond such link elements, additional link elements might be
included in the feed elements.
Only one rights and subtitle element is allowed for each feed element.
The entry Element
Atom news can be provided by the entry element. It can be a child of the feed element or a stand-alone, top-level
element within the feed. The entry elements must have a minimum of one author element except when a source
element is provided in the entry that has an author element or the feed element contains an author element.
Optionally, entry elements have any number of category elements. The entry elements might have a maximum of
one content element. Another optional subelement of the entry element is the contributor . An arbitrary number of
contributors can be provided.
The entry elements must have an id element.