Your subject says "Excel" but in the body you write about XML ??
Excel should be no problem as Mathcad can read and embed Excel files out of the box.
Concerning XML you'd be forced to write your own parser in Mathcad.
1) Open the XML Data File in Excel. Excel can do this.
2) Check the Excel file to see the import is what you want.
3) Save the Excel file as a *.xlsx excel workbook.
4) Open Mathcad Prime
5) Go to menu item Input/Output and you will see READEXCEL as an option use this.
6} A dialog box opens where you can browse for the excel file to read. It reads it into a Prime matrix.
You mentioned "date" in your question.
Mathcad Prime has no date value.
Here are some useful date functions. It explains the difference between Excel and Georgian day number.