The nine days that comprise the nine thithis from Prathamai to Navami in the Sukla paksham (waxing moon phase) of the Purattaasi maasam (mid September to mid October) of each year are collectively referred to as Saradha Navaraathri.
A similar set of nine days occur earlier in each year in the March to May timeframe. These nine days are known as Vasantha Navaraathri.
In general, the Siddhas treat the nine thithis from Prathamai to Navami of each moon phase as Navaraathri. Thus there are 24 to 25 Navaraathri periods that occur each year. Of these the aforementioned two are very improtant.
The Universal Mother manifests Herself as Durga, Lakshmi and Sarasvathi and worships the Universal Lord during all Navaraathri days. Thus it's important that we worship the Universal Lord and the Durga, Lakshmi and Sarasvathi manifestations of the Universal Mother in the Navaraathri time period.
The time period from Oct/9/99 to Oct/19/99 is the Saradha Navaraathri period for the Pramaadhi varusham (April 1999 to April 2000). It starts at 1135 hours GMT on Oct/9/99 and lasts till 0518 hours GMTon Oct/19/99. Please refer to the Agasthiar spiritual calendar for the exact times in your timezone.
The Siddhas refer to the Saradha Navaraathri of the Pramaadhi year as Saakambari Navaraathri in honor of the Universal Mother in Her manifestation as Sri Saakambari Devi. Since the Pramaadhi year occurs once in 60 years, Saakambari Navaraathri occurs once in 60 years too.
Sri Saakambari is that manifestation of the Universal Mother who is in charge of the entire plant kingdom. Since a substantial number of life forms, including a substantial number of humans, depend on the plant kingdom for their food, it's important that we worship Mother Saakambari every day. In fact, it's the duty of everyone of us to honor Mother Saakambari at least once everyday.
Ah! The pleasure of good food! But before we experience this pleasure, we must honor Mother Saakambari! This is the advice of the Siddhas. And it's particularly important that we honor Mother Saakambari during the nine days of the Navaraathri from Oct/9/99 to Oct/19/99.
During these nine days, Mother Saakambari worships the Universal Lord on behalf of all life forms everywhere. Worshipping the Mother and the Lord during these nine days amounts to participating in the Mother's worship process. This is a unrivalled privilege in the world of spirituality. Thus those who are wise will put these nine days to good use by engaging themselves in worship of the Universal Mother and the Lord.
Pages 11 to 21 of the Oct/99 issue of Sri Agasthia Vijayam, the Ashram Tamil monthly, describe Saakambari Navaraathri and the special worship procedures that need to be performed on each of the nine days. Please follow the instrutions that have been spelled out therein.