To represent a negative offset, ISO 8601 specifies using a minus sign. If the interchange character set is limited and does not have a minus sign character, then the hyphen-minus should be used. ASCII does not have a minus sign, so its hyphen-minus character (code is 45 decimal or 2D hexadecimal) would be used. If the character set has a minus sign, then that character should be used. Unicode has a minus sign, and its character code is U+2212 (2212 hexadecimal); the HTML character entity invocation is codice_1.