Hi, ushankar!
You can't have stored the date&time of last saving within a cell, because d&t is updated by the operating system and that's after many internal operations, which not include storing a value within a cell from Excel. But you can retrieve it at next open time (or when you want) using the function FileDateTime.
You can use this statement:
Worksheets("X").Range("A1").Value=FileDateTime(file_path)
What you can do from Excel is get a fairly accurate approach to that value, with the event Workbook_BeforeSave (from the VBA editor, double click on ThisWorkbook, Workbook, BeforeSave from the right drop down box).
You can place these statements there:
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Application.EnableEvents=False
Worksheets("X").Range("A1").Value=Now()
Application.EnableEvents=True
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The Application.EnableEvents are not necessary if you don't have any Worksheet or Workbook Change events with code that might interrupt saving process, but leaving them you're sure they won't interfere.
Regards!