What does ca mean?

[v0031]

Soldier shares a banana with a goat during the battle of Saipan, ca. 1944

[v0031]

http://en.wikipedia.org/wiki/Circa

Thanks, sorry for still being puzzled after seeing the wiki explaination.

[Tetro Kornbluth]

Sometimes it is written just as c.

For example Soldier shares a banana with a goat during the battle of Saipan, c.1944

[Mr. Morden]

It's a term used frequently when you have a photograph but don't know exactly when it was taken.  If the caption on a photo says "ca. 1944" (short for "circa 1944"), that means that we don't know for certain what year the photo was taken in, but 1944 is the best guess.