http://astrobix.com/festivals_of_india/holi/holi_holaastak.aspx
According to the lunar month (Chandra Maas), Purnima of Phagun Maas is celebrated as Holika festival. Holashtak witnesses the arrival of Holi. Holashtak is known as a poster, informing about the arrival of Holi festival. Looking at the literal meaning of Holashtak, we find Hola + Ashtak, which means eight days before Holi, that is Holashtak. Basically, we can see that holi is a festival of nine days instead of a single day. On the day on Dhulendi with colors and Gulal, this festival comes to an end.
Things that Shouldn't be Done During Holashtak
This prohibition is from the day of Holashtak to Holika Dahan. As per the name Holashtak begins eight days before Holi.
In the mid of Holashtak, none of the rituals(Sanskar) is done out of the 16. Even, before the cremation, ‘Shanti Karya’ is performed. Since, the 16 rituals are not allowed in these days, hence, this period is counted as inauspicious.
