Using format-dateTime in BusinessWorks 5.x and 6.x is different.
If you print "tib:format-dateTime("yyyyMMddHHmmss",current-dateTime())" in BW 5.x, you will see an output resembling 20150807105204. This is as expected.
If you try to use the same string in BW6.x like format-dateTime(current-dateTime(), "yyyyMMddHHmmss"), it will print "yyyyMMddHHmmss" and not throw an error. This is not as expected.