Although it looks like a completely new story at first, chinese horoscope is not so different from western zodiac, its monthly signs being a good example of this.

Both of them are determined by the position of the Sun on certain areas of the Sky during the year, and the truth is that anyway you look at it, there is just one Sun and one Sky, so basically it's a matter of deciding the names to give to those astrological influences caused by the position of the Sun reltive to the Earth.

To see the monthly chinese sign of a person just use the natal chart form and look in month's column, also you can use this table where you can see how the western signs complement the chinese ones:

	chinese solar month	Chinese solar signs (dates vary slightly from one year to other)				Western Sign
	7/dic 6/ene	Rat : its central point (from 21 to 24 December) is defined by the winter solstice in the Northern Hemisphere
					21/Dec
	4/feb
						20/Jan
	6/mar
						20/Feb
	5/abr	Rabbit: its central point is defined by the Spring Equinox
						21/Mar
	6/may
						21/Abr
	6/jun
						22/May
	8/jul	Horse: its central point is defined by the summer solstice
						22/Jun
	8/ago
						23/Jul
	8/sep
						22/Ago
	9/oct	Rooster: its central point is defined by the autumn equinox
						23/Sep
	8/nov
						23/Oct
	7/dic
						23/Nov

Obviously the characteristics of each Chinese monthly sign are the same of the corresponding annual months, with the detail that their influence is not "all or nothing" but something that goes up and down and changes from one sign to the next progressively.

In the above table I notice the central points of several signs because those are the moments where the characteristics of the sign in question are stronger.

And how does this fit with the 12 signs of Western Astrology? Very simple, it turns out that the changing points of western signs coincide with the central points of chinese signs, for example, the central point of the snake, is que changing point between taurus and geminis.

When I have time I'll make a sketch to illustrate the idea, but basically it is as if there were 24 solar signs, which are formed alternating one chinese and one western sign depending on the date.

At first you may think that western signs are too much different from chinese signs, but if you look closely to the characterisitics of each of them, specially when one sign change to the next, you will see that they hace mucho more points in common that it seems at first, it can not be otherwise because both astrological systems refer to the same Sun on the same areas of the sky at the same time... so basically what they do is talk about the same thing with different words.