Solution : https://service.sap.com/sap/support/notes/1015249 (SAP Service marketplace login required)
Key words :
required support package levels, correct date format information, latest support package, specfied date properly, single digit week, cl_abap_datfm=>conv_period_ext_to_int assumed, date format, single digit, input date, class cl_abap_datfm
Related Notes :
| 831333 | Enable Japanese emperor, Islamic, and Farsi date format |