Have a look at the trading.h file and find the CONTRACT struct which defines what each field in the .t8 file needs to look like. Quote datetime field DataDate in your file is of DATE format so your '%Y-%m-%d' string format will work. However the Expiry is a type Long of format YYYYMMDD so you need to use an "%i" string format. Also note that only those fields in the struct are necessary for the parser as those are the only ones that end up in your .t8 file.