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According to many grammar textbooks, present perfect tense should not be used with specific time expression. Therefore, it is grammatically wrong to say "I have sold my house on 10 December 2018."
However, I often see this type of sentence in the writings from the United States:
In witness whereof, I have hereunto set my hand and affixed the Official Seal of said City this 26th day of August, 1954.
Questions:
Does the word 'this' make it an exception that 'present perfect tense' can be used with specific time expression in this construction?
or
Is the use of present perfect tense with specific time expression allowed only in American English?

In this instance it is the use of old English, as used on official documents.

Oh, that could be the possibility! Thank you Ajarn Jaraswat.