This will add a template function that calculates the number of days from today until a given date.
silverbullet.registerFunction("daysTillDate",(date) => {
const parsedDate = Temporal.PlainDate.from(date)
const now = Temporal.Now.plainDateISO();
return now.until(parsedDate, { largestUnit: 'days' }).days
})
{{daysTillDate(nextWeek())}}