The calculations needed to perform a time jump are all handled inside a big monstruous .xlsx file with a bunch of Microsoft Excel formulas. The reason it was done in Excel is because it has the wonderful power of holding in a lot of data in its spreadsheets and do a lot wonders of calculations. All time machines comes with Microsoft Windows and Microsoft Excel installed.
Someone tried to make engineers and physicists learn actual programming. The result was that some of them were able to learn VBA and used it to write macros in Microsoft Excel. After that, they considered that they already know enough of programming and have no spare time with playing with those boring
If...End If and
For...Next toys any further because they already have too much actual hard work to do with physics and engineering.
Engineers and physicists are people that never even heard about the existence of a RDBMS. If they ever hear someday about the existence of a thing called RDBMS, then they will never have a clue about what it is or what it is the purpose. If in some full moon night at Friday 13th, they get it, then they would never be willing to learn it because knowing Microsoft Excel is already enough. If they learn about RDBMS, they will always keep still using Excel because they'll never be able to decode that strange alien language called SQL. If they eventually learn SQL, they will try to use SQL with Microsoft Access as a thing to input data into Excel spreadsheets and never feel any need to go any further with this. If they eventually realize what is the purpose of a RDBMS, how to use proper SQL and how to correctly wire it to a software system and what is the benefits of that design, then they immediately suffer a simultaneous hearth attack and stroke and die.
Someone proposes the idea of calling some actual software developers to give a look onto that. After seeing a lot of incomprehensible gibberish in a big mess of Excel formulas salted and peppered with some VBA macros, all of them quickly resigned their jobs and went work in some other jobs which was paying much higher salaries for actual programming in Java, C#, Pyhton, PHP, Node.JS or anything else, as long as it has nothing to do with Excel nor VBA.
So, the sad conclusion is that it is impossible to create a time machine without using Microsoft Excel.
Dates in Microsoft Excel starts at January 1st, 1900. Negative dates are used as a hack to travel to the future instead of going to the past. This could perhaps be changed, but nobody know for certain where in the sea of Excel formulas and VBA macros that sort of thing is handled.
Someone also had the idea of going to February 29, 1900. That person landed here.