If you are handling data from sheets it might be useful to use the same logic as is available in the worksheet for common tasks rather than reinventing them. Dates and Times are especially complicated as JavaScript dates are not good with timezones and date arithmetic, especially since spreadsheets and scripts can exist in different timezones from each other. I’m using Temporal – dates, times and timezones and the proposed new Date system for ECMAScript to emulate what Sheets functions do, and I’ll go through the implementation as a learning aid for Temporal as much as a documentation of the functions.
