Feng shui cycle

Cycles or periods in feng shui last about 20 years.  Each cycle has a ruling star from 1 - 9 which will repeat itself after 180 years (20 * 9).  Houses built during these periods, are ruled under that star's influence. So you may hear a house is a period 7 or period 8 house. This refers to the construction date of the house. 

Cycles also change in February with Chinese new year.

Cycle star	Periods
1	1864 - 1883
2	1884 - 1903
3	1904 - 1923
4	1924 - 1943
5	1944 - 1963
6	1964 - 1983
7	1984 - 2003
8	2004 - 2023
9	2024 - 2043
1	2044 - 2063

As of February 2004 we are in period 8.  So houses constructed during these years are period 8 homes.

The cycles numbers are very important since based on this information the birth chart of your site, house or office is formed. 

It is possible to change the period of a house, but major renovations are needed in which part of roof has to be removed and the air has circulate all the way to the basement of the house!