In case someone likes to further process Olive files and relies on formatted input (like me), the following might be a strange feature of Olive (I haven't checked thoroughly): Iff a problem has more than one author and year-month in the date field, the month is formatted as date: YYYY-0M, otherwise as date: YYYY-M (iff M<10). Normal users can safely ignore this.
In case someone likes to further process Olive files and relies on formatted input (like me), the following might be a strange feature of Olive (I haven't checked thoroughly): Iff a problem has more than one author and year-month in the date field, the month is formatted as date: YYYY-0M, otherwise as date: YYYY-M (iff M<10). Normal users can safely ignore this.