private void checkDateTime() throws FormatFlagsConversionMismatchException {
if (precision != -1)
throw new IllegalFormatPrecisionException(precision);
if (!DateTime.isValid(c))
throw new UnknownFormatConversionException("t" + c);
checkBadFlags(Flags.ALTERNATE, Flags.PLUS, Flags.LEADING_SPACE,
Flags.ZERO_PAD, Flags.GROUP, Flags.PARENTHESES);
// '-' requires a width
if (width == -1 && f.contains(Flags.LEFT_JUSTIFY))
throw new MissingFormatWidthException(toString());