Can you explain a bit more ? In NPRINTING you can design a report in the 'excel template' (use MS Excel to design the report) or when you design a report using the different editors , you can run the report to generate an excel output ?
If you need to run the report to generate an excel output, it probably makes sense to design the report in the excel template and you use the excel native formatting options to create the header. Here is a sample of a repeating header from the nprinting knowledge base.
Also, if you use the 'pixel perfect' editor you can drag and drop text, data, charts directly into the 'header', 'body' , or 'footer' area of a report . Whether or not you run the report as an excel output or other output (PDF) is separate to the template editor you choose to create the report in.
NPrinting Tags or not currently supported in MS Office excel, word, pptx headers and footers.
You can use the native Excel functionality to add the date into the header. The date format can be set to various types; some of this will depend on the date settings of the local machine of the person who opens the Excel file.
As Frank noted, it's not possible to put QlikView variables, formulas or fields into Excel Headers or Footers in NPrinting.