Solution : https://service.sap.com/sap/support/notes/197254 (SAP Service marketplace login required)
Key words :
system issues error message ke 507 'special period $, special period reason, valid -> check entry', normal fiscal year, fiscal year variant, post fi documents, special period, standard system, special periods, variant set
Related Notes :
| 672255 | Shortened fiscal year/changing fiscal periods |