Hi Nes..I have heard and looked at the chinese calender sex prediction once I was pregnant the first two times. I sort of used it to conceive our third. The Calender was right on all three occassions for me.
Two boys and then a girl. With the boys, we were not regularly DTD, so it could be a week two without, then DTD.
I didn't alter my diet, we did DTD every second day and when I checked the calender it predicted girl. The U/S was only 90% sure of girl, she is in fact a girl.
Dr Shettles method is supposed to be good as well. Worth a google.
Good luck.