According to the Hindu calendar there are two Pakshas in a month, one is Shukla Paksh and the other is Krishna Paksh . Every Paksh has fifteen days. But due to Vriddhi Tithi (additional Tithi), there are 16 days in a Paksh. And due to the Kshaya Tithi, there remains 14 days in a Paksh.In a very few cases there are two Kshaya Tithis in a Paksh and as a result of it there remains only thirteen days in a Paksh due to two kshaya Tithis.This thirteen days Paksh is known as Vishva Ghastra Paksh.The Paksh of thirteen days is considered as an inauspicious period.
During this Paksh, the auspicious tasks like marriage,engagement, starting a new business , purchasing a new vehicle etc.are prohibited. But the tasks which have been started in the shubh muhurat before the starting of the thirteen days paksh and are in progress, have no bad effect of this paksh so they should not be stopped.
Other Posts you will like to read -
(5.3.13) Meen Sankranti - Meen Mal Maas period.
(5.3.15) Combustion of Guru ( Jupiter ).
(5.3.27) Combustion of Shukra ( Venus )
(4) Hari Shayan period.
(5.3.13) Dhanu Sankranti ( Dhanu Mal Maas )
(5.3.16) Thirteen days Paksh ( Pakhawara )
(5.3.26) Singhast Guru (Guru in the singh Raashi)