interface DateSqlInterface

interface DateSqlInterface {
    
    /**
     * Returns a native database expression for a given field.
     *
     * @param string $field
     *   The query field that will be used in the expression.
     * @param bool $string_date
     *   For certain databases, date format functions vary depending on string or
     *   numeric storage.
     *
     * @return string
     *   An expression representing a date field with timezone.
     */
    public function getDateField($field, $string_date);
    
    /**
     * Creates a native database date formatting.
     *
     * @param string $field
     *   An appropriate query expression pointing to the date field.
     * @param string $format
     *   A format string for the result. For example: 'Y-m-d H:i:s'.
     *
     * @return string
     *   A string representing the field formatted as a date as specified by
     *   $format.
     */
    public function getDateFormat($field, $format);
    
    /**
     * Applies the given offset to the given field.
     *
     * @param string &$field
     *   The date field in a string format.
     * @param int $offset
     *   The timezone offset in seconds.
     */
    public function setFieldTimezoneOffset(&$field, $offset);
    
    /**
     * Set the database to the given timezone.
     *
     * @param string $offset
     *   The timezone.
     */
    public function setTimezoneOffset($offset);

}