I think that when I applied Armando patch to use the more portable Add_Delta_YMD() (instead of using advanced features of GNU date) that somehow the change to ($day+7) was missed. With Add_Delay_YMD(), $day should be properly set already, and timelocal() cannot already invalid values.

I never caught before because to do so you must have at least one project having a weekly export and export is still very scarcely used.

sv_export complains hourly with something like:
Day '37' out of range 1..31 at /usr/local/bin/sv_export line 528

Apparently there's something wrong when adding '7' to the current day.