How many {inception} are for {Gregorian calendar} ?
How many inception are there in the {Gregorian calendar} ?
SELECT (COUNT(?obj) AS ?value ) { wd:Q12138 wdt:P571 ?obj }
SELECT (COUNT(?obj) AS ?objs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q12138> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P571> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
} 

Which is the number of inceptions in the Gregorian calendar?