Applicants should not exclude non-working days, as this can result in the one-month secondment not being eligible; however, the secondments must always be proofed by documentation (boarding passes - MSCA Financial Guidelines, p. 41)
“− for MSCA-SE:
− proof that the secondment was eligible (e.g. agreement for the secondment, travel documents and/ or access rights for the host organisation's premises to show the duration of the secondment, lab books, registration documents, scientific articles, library records to demonstrate engagement in research and innovation activities)”