@muuos What do you have in mind? There is no such thing as negative time. You could switch to the 1904 date system, as that will allow for "negative time", but it will shift all your dates by four years. For example, 1 January 2021 in the 1900 system becomes 2 January 2025 in the 1904 system. Same day numeral, but a different date being displayed.