h1. Dates

The OpenAtlas data model can store chronological information for certain entities and properties. 
In general it can document a timespan for the begin and a timespan for the end of those. The smallest timespan unit possible is one day. There are no restrictions regarding the length of these time spans.

E.g. if you do not know the exact date of an actor's birth, but only that she/he was born at the earliest in 800AD and at the latest before 805AD, this timespan would range from Jan. the 1st, 800 to Jan. the 1st, 805. Given that person died on the 23rd of Aug. 877 you would only enter that day as and end-date. In the user interface this case would look like:

!date.jpg!

The system automatically creates the correct timespan given by the bounding dates provided by the user:

!date1.jpg!

This way you can store chronological information as precise as possible or as fuzzy as necessary. Also it is possible to add a comment on the date e.g. "circa".
The same principle works for all of the following entities and properties:

 Entities
  Physical Things
     Places (E18)
       Features (E18)
       Stratigraphic Units (E18)
       Finds (E22)
   Actors
       Persons (E21)
       Groups (E74)
       Legal Bodies (E40)
   Events
       Activity (E7)
       Acquisition (E8)
       Production (E12)
       Destruction (E6)

 Properties that link actors to Events
   performed (P14)
   participated in (P11)
   acquired title through (P22)
   surrendered title through (P23)
 Properties that link actors to Actors
   has relationship to (OA7)
   is current or former member of (P107)

The data is stored in the table model.entity, i.e. model.link in the fields begin_from, begin_to, begin_comment, end_from, end_to, end_comment as timestamps.
Depending on class of the entity, that is to say, the domain and range classes of the link, these dates can be mapped as time primitive (E61) entities within the CIDOC CRM.
The respective paths are the following:

E77 Persistent Item begin linked with a E61 Time Primitive:
* Domain: E77 Persistent Item
* Range: E61 Time Primitive

<pre>
E77 (Persistent Item) - P92i (was brought into existence by) - E63 (Beginning of Existence) - P4 (has time span) - E52 (Time Span) - P81 (ongoing throughout) - E61 (Time Primitive)
</pre>

*Example:* [Holy Lance (E22)] _was brought into existence by_ [forging of Holy Lance (E12)] _has time span_ [Moment/Duration of Forging of Holy Lance (E52)] _ongoing throughout_ [0770-12-24 (E61)]

E77 Persistent Item end linked with a E61 Time Primitive:
* Domain: E77 Persistent Item
* Range: E61 Time Primitive

<pre>
E77 (Persistent Item) - P93i (was taken out of existence by) - E64 (End of Existence) - P4 (has time span) - E52 (Time Span) - P81 (ongoing throughout) - E61 (Time Primitive)
</pre>

*Example:* [The one ring (E22)] _was destroyed by_ [Destruction of the one ring (E12)] _has time span_ [Moment of throwing it down the lava (E52)] _ongoing throughout_ [3019-03-25 (E61)]

E21 Person's Birth linked with a E61 Time Primitive:
* Domain: E21 Person
* Range: E61 Time Primitive

<pre>
E21 (Person) - P98i (was born) by - E67 (Birth) - P4 (has time span) - E52 (Time Span) - P81 (ongoing throughout) - E61 (Time Primitive)
</pre>

*Example:* [Stefan (E21)] _was born by_ [birth of Stefan (E12)] _has time span_ [Moment/Duration of Stefan's birth (E52)] _ongoing throughout_ [1981-11-23 (E61)]

E21 Person's Death linked with a E61 Time Primitive:
* Domain: E21 Person
* Range: E61 Time Primitive

<pre>
E21 (Person) - P100i (died in) - E69 (Death) - P4 (has time span) - E52 (Time Span) - P81 (ongoing throughout) - E61 (Time Primitive)
</pre>

*Example:* [Lady Diana (E21)] _died in_ [death of Diana (E69)] _has time span_ [Moment/Duration of Diana's death (E52)] _ongoing throughout_ [1997-08-31 (E61)]

E2 Temporal Entity (also property) begin linked with a E61 Time Primitive:
* Domain: E2 Temporal Entity
* Range: E61 Time Primitive

<pre>
E2 (Temporal Entity) - P4 (has time span) - E52 (Time Span) - P81 (ongoing throughout) - E61 (Time Primitive)
</pre>

*Example:* [Thirty Years' War (E7)] _has time span_ [Moment/Duration of Beginning of Thirty Years' War (E52)] _ongoing throughout_ [1618-05-23 (E61)]

E2 temporal entity (also property) end linked with a E61 Time Primitive:
* Domain: E2 temporal entity
* Range: E61 Time Primitive

<pre>
E2 (temporal entity) - P4 (has time span) - E52 (Time Span) - P81 (ongoing throughout) - E61 (Time Primitive)
</pre>

*Example:* [Thirty Years' War (E7)] _has time span_ [Moment/Duration of End of Thirty Years' War (E52)] _ongoing throughout_ [1648-10-24 (E61)]