Bhadra

To this day, the Hindus observe these 16 lunar days.

falling during the Hindu month of Bhadrapada or Ashwin, which is invariably around September to October.

And what do they do? They offer Tarpan, which is offering water mixed with sesame seeds to the departed ancestors.

They do Shraddha, which is performing simple prayers and offering home-cooked food and charity.

And of all the new moons of a year...

the most important new moon is that of the lunar month of Bhadrapada, which is usually in September.

Because the fortnight just before that new moon is called the Pitru Paksha.

It's called the fortnight of the ancestors.

If anyone tells that Garga Sangita is his reason, that Krishna took birth on 6th day, 16th, in coming month.

Bhadra took last 16th.

In Bhadra, not in dark night, but in white night, on 6th day.

So how you can deny? Because it is written in Gargasam Gita.

It has been told for other manmantras.