Solved
Is analytics t variable zero based?
According to http://microsite.omniture.com/t2/help/en_US/sc/implement/query_parameters.html, the t variable is in the format
dd/mm/yyyy hh:mm:ss D OFFSET
When I look at the actual request made, it is 19/0/2015 11:1:5 1 480
Is the month January represented by the 0 or is that a bug in the library?