@Yudhisteer_Chintaram1 - Could you please try this…
dtdate.AsEnumerable().ToList().ForEach(Sub(row) row("ASN Shipment Date")=Datetime.ParseExact(Datetime.FromOADate(cdbl(row("ASN Shipment Date"))).ToString("dd/MM/yyyy"),"dd/MM/yyyy",CultureInfo.InvariantCulture))
For me this is giving the output in dateformat but in M/dd/yyyy format, may be it will work for your case based on the country.
Please try and let me know.