adjust time counter to increment with 30 seconds per frame

Hi all,

I am doing time-lapse video, and mostly with 30 seconds intervals.
When I import the video into fcp I can add a time generator, but this will increment as if it was shot at 25 frames/second, the native speed of the video recorder.

Is there a way (or a plug-in to have it increment with 30 seconds per frame?
i.e. frame 1 is 0:0:0:0; frame 2 is 0:0:30:0 frame 3 is 0:1:0;0 etc??

Thanks for any suggestions...

M