I'm working at the moment finding places of birth for photographers who have birthdates but lack locations (my query is below). Ultimately I'll be comparing WD's photographer info to my own database of photographer biographies. This leads me to a few questions regarding dates:

How can I query out the date data in plain language (20 July 1982 vs. 1982-07-20T00:00:00Z)?

I need this so I can distinguish between someone actually born January 1, 1900 and someone whose birth date is given as simply 1900, or someone with a date given simply as 19th century.

How do folks feel about giving lifedates as centuries (born: 19th century)? I personally would not do it. In my own database, if lifedates are not known we give "active" dates. For example I would have 
Alexander Möhlen (German, active 1900s-1910s).

Is there a concept such as "Period of Activity" that could be used, or would others find this desirable?

Is there a way to record uncertainty in dates (circa or ca.)?

Many thanks in advance,
David


PREFIX wd: <http://www.wikidata.org/entity/>
PREFIX wdt: <http://www.wikidata.org/prop/direct/>
PREFIX wikibase: <http://wikiba.se/ontology#>
PREFIX p: <http://www.wikidata.org/prop/>
PREFIX v: <http://www.wikidata.org/prop/statement/>
PREFIX q: <http://www.wikidata.org/prop/qualifier/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>

SELECT ?photographer ?photographerLabel ?photographerDescription ?dob WHERE {
   ?photographer wdt:P106 wd:Q33231 .
   ?photographer wdt:P569 ?dob .       
  FILTER NOT EXISTS { ?photographer wdt:P19 ?pob .} 
  
                       
  SERVICE wikibase:label {
     bd:serviceParam wikibase:language "en" .
 }
} Order by ?photographerLabel