Question Summary:
In behisti zewar which is a very authentic Hanafi book of fiqh problems ,it is mentioned that if a man or woman…

Question Detail:

In behisti zewar which is a very authentic Hanafi book of fiqh problems ,it is mentioned that if a man or woman doesnot know in ramadan days that sahoor time has ended and he keeps on eating his sehri(and he is totally in dark about it) ,the qaza of that fasts is not wajib on him(not obligatory) because he had a zero understanding of the time(thus he is not sinful).However it is good if he keeps those fasts again.What is your opinion about it?

Answer :

In the name of Allah, Most Gracious, Most Merciful
Assalaamu `alaykum waRahmatullahi Wabarakatoh
On the sister’s request, we looked into Bahishti Zewar and found the following ruling:
A person woke up a bit late and thought that there is time left. On this assumption, he made sehri. Later he learnt that he had made sehri after dawn. His fast will not be valid. He should make qada but kaffarah will not be wajib. However, he should still abstain from eating and drinking anything and remain like any normal fasting person.
Heavenly Ornaments Vol: 1 Pg: 287 (Zamzam publishers)
We also looked into the urdu version and found the exact same ruling mentioned above.
Bahishti Zewar Pg: 210 (Maktabah Thanwi Deoband)
Moreover, other authentic Hanafi books also have the ruling that qada will be wajib in such situations.
( أو تسحر أو أفطر يظن اليوم ) أي الوقت الذي أكل فيه ( ليلا و ) الحال أن ( الفجر طالع والشمس لم تغرب )
( قوله : أو تسحر إلخ ) أي يجب عليه القضاء دون الكفارة ؛ لأن الجناية قاصرة وهي جناية عدم التثبت لا جناية الإفطار ؛ لأنه لم يفسده
Radul Muhtar Vol: 2 Pg: 405 (H.M. Sa’eed Company)
Therefore, there is a possibility that the matter had been misunderstood. However, it was very wise of you to refer to an Islamic scholar than taking the matter in your own hands. We acknowledge your zeal for knowledge and advice you to always refer to Islamic scholars whenever there is a doubt. 
And Allah knows best
Wassalam
Ml. M. Jawed Iqbal,
Student Darul Iftaa
Checked and Approved by:
Mufti Ebrahim Desai
Darul Iftaa, Madrassah In'aamiyyah