framework/validators/DateValidator.php
private function parseDateValueFormat($value, $format)
    {
        if (is_array($value)) {
            return false;
        }
        if (strncmp($format, 'php:', 4) === 0) {
            $format = substr($format, 4);
        } else {
            if (extension_loaded('intl')) {
                return $this->parseDateValueIntl($value, $format);
            }

            // fallback to PHP if intl is not installed
            $format = FormatConverter::convertDateIcuToPhp($format, 'date');
        }

        return $this->parseDateValuePHP($value, $format);
    }
private function parseDateValueFormat($value, $format)
    {
        if (is_array($value)) {
            return false;
        }
        if (strncmp($format, 'php:', 4) === 0) {
            $format = substr($format, 4);
        } else {
            if (extension_loaded('intl')) {
                return $this->parseDateValueIntl($value, $format);
            }

            // fallback to PHP if intl is not installed
            $format = FormatConverter::convertDateIcuToPhp($format, 'date');
        }

        return $this->parseDateValuePHP($value, $format);
    }
Parses date string into UNIX timestamp.

@param string $value string representing date
@param string $format expected date format
@return int|false a UNIX timestamp or `false` on failure.