convert_format:
          numeric_format | datetime_format

numeric_format:
          "[<< | >> | ><]['text' | $][- | (][#,]#[.#[#]...][e | E]['text' | $ | %]"

datetime_format:
          "[<< | >> | ><]['text' | spchar | date_code | time_code]..."

date_code:
          m | mm | mmm | mon | mmmm | month
     |    d | dd | ddd | dddd | day
     |    yy | yyyy

time_code:
          h | hh | m | mm | s | ss | .f[f]... | [a/p | am/pm | A/P | AM/PM]