Actually no, Year Zero for HD would be 2009. Planet of the Dead was the first episode shot in HD, followed by The Waters of Mars and The End of Time - all three were shot in 1080i50. (All 3 have been released on Blu-Ray as well, along with an upconverted version of The Next Doctor, which was shot in SD.)
Series 5 is the first full series to be shot in HD, though, you're right about that.