'ca.' is the abbreviation of 'cirka' meaning 'about, approximately'.

Hej Rina. Thank you for expanding on these answers--very helpful.

And it is not only used to indicate a date but anything, mostly with numbers. En flaske vand koster ca. 10 kr. Bordet er ca. 1,5 m (meter) langt Vi ses ca. kl. (klokken) 12

Phil: You are totally right :) Bruce: It spells "cirka" but mostly we use "ca."

Hi, Phil. It's from a long sentence but a fragment of it is "...for ca. 14.000 år siden..." There's little doubt that "ca." is used here as we would use it in written English. I am hoping to find out the Danish spelling, which could be circa, cirka, or something else. Thanks.