There is confusion regarding the date/date for performing Upakarma,called Avani Avittam .
It is one of the major festivals for Brahmins,though all the three varnas,Brahmana,Kshatriya and Vaisyas must perform.
It is natural for us to get confused about Hindu Festivals,as ,I might add,to my regret,we are familiar with only English Calendar and not our calendar/s.
Hindu calendar follows both Surya Maanasa and Chandra Maanasa,that is Time calculated on the basis of Sun and Moon.
The Gregorian Calendar Calendar underwent a lot of changes,including changing the calendar on the whims of a Ruler(Julius Caesar).
It would be of interest to note that Britain was following Our Hindu Calender!
Now to Upakarma,Avani Avittam dates.
The Yajur Upakarma is to be celebrated on 6th September 2017,as the earlier day happens to be day when Grahana,Eclipse takes place.
Rig Upakarma August 28th,(Aadi12th),
Sama Upakarma,August 25th( Avani 9th),
This decision has been announced by Kanchi Kamakoti Mutt.
Generally,the Rig Vedis,Yajur and Samavedis perform on different days.
Details are given towards the close of this article.
Rigvedis generally follow Suryamaanasa and hence give importance to Nakshatra,in this case,Sravana Nakshatra.
Yajurvedis generally follow Chandra Maanasa,therefore they give importance to Thithi,the waxing and waning of the Moon.
So they perform Upakarma,Avavi Avittam on the Full Moon Day,Pournami.
However,one must remeber that by tradition,Upakarma is not performed if Grahana occurs on the Upakarma Day.
Next Nakshatra or next same Thithi is declared to be auspicious for performing Upakarma.
One may observe that Upakarma is basically equivalent to the beginning of Academic Year,that’s all.
That it should not be performed on Grahana day is something I do not find any Smriti mentioning it.
Readers may send information.
Smritis declare that any new endeavor or Auspicious activity undertaken on Grahana day would be successful and Mantras chanted during Grahana(Eclipse) would yield thousand fold result.
So this practice of changing days on account of Grahana seems not sound,barring the tradition.
For details on Vedic Syllabus and Upakarma.
‘Normally the child is sent for learning at the age of Five after Yagnayopaveeda ceremony to the teacher where the child stays and learns.