Converts an internal representation of time into a string representation of time.
Writes a string corresponding to the elapsed time t into the location str, making the appropriate conversions for the clock system designated by zone. The precision of the clock seconds field is controlled by the precision parameter, which determines the number of digits written beyond the decimal point. Negative values of precision result in suppression of increasing numbers of clock and date fields, up to values of -5. For example, a precision of -1 will suppress the seconds field, and a precision of -5 (or less) will cause only the year to be written.