Comment 8 for bug 591948

I have similar problems that also manifest when building graphs covering multple months:
=> the labels displayed are incorrects: i can get twice the same month and after every is shifted

I looked at the code in render/glyph.py and compared it to rrd_graph.c. I found rrd is now using find_first_time and find_next_time internal functions to define where grids and labels are to be drawn. Maybe we could adapt glyph.py to work accordingly.