pdfcreationdate format(s)

Hi,

 it seems there are two versions of \pdfcreationdate out there.

 All those that I use output something in the form
   D:20171205171912+01'00'
 And that is what the manual describes

 but I have trouble sharing code with some other installs where it
 seems it can output something like
   D:20171205162354Z

 Does anyone know which versions of pdftex output the second version,
 and how one can tell which one will be output (with a test, e.g.)?

Thanks,
 Thierry