Dim myDate As Date, strDate As String
myDate = CDate("2021-01-28")
strDate = Format(myDate, "YYYY-MM-DD")

Excel formula to turn a date/time into text:
=TEXT(A1,"DD/MM/YYYY hh:mm:ss AM/PM")
'Reference:
' https://support.office.com/en-us/article/text-function-20d5ac4d-7b94-49fd-bb38-93d29371225c
'---------------------------------------------------------------------------------------------
'VBA function to do the same thing:
Function DateToText$(dbl#) DateToText = Format(dbl, "DD/MM/YYYY hh:mm:ss AM/PM")
End Function