Hi Ranjith,
That is what I understood.
What I wanted to say is that the only way to set that field to 01.01.0001 in the specification workbench (without any custom logic) is to change the key date (or working with a change number with that key date) and then change any specification data.
I am not aware of any other action that would set this date.
Can you reproduce the issue?
Regards,
Andreas