time.minutes-between

export function minutesBetween(startDate: string, startTime: string, endDate: string, endTime: string): number

import { minutesBetween } from "#fune/time.minutes-between@^1";

import { epochDayFromIso } from "./dates_add_days.ts";  ← from dates.add-days ^1.0.0 · built alongside by fune

function minuteOfDay(time: string): number {
  const ok =
    typeof time === "string" &&
    time.length === 5 &&
    time[2] === ":" &&
    [0, 1, 3, 4].every((i) => time[i] >= "0" && time[i] <= "9");
  const hours = ok ? Number(time.slice(0, 2)) : -1;
  const minutes = ok ? Number(time.slice(3, 5)) : -1;
  if (!ok || hours > 23 || minutes > 59) {
    throw new RangeError(`"${time}" is not a time of day (HH:MM, 00:00 to 23:59)`);
  }
  return hours * 60 + minutes;
}

/**
 * Minutes from one local date and time to another: the difference between two
 * wall-clock readings. It knows nothing of time zones or daylight saving, so
 * across a clock change it differs from real elapsed time by the change.
 */
export function minutesBetween(startDate: string, startTime: string, endDate: string, endTime: string): number {
  const days = epochDayFromIso(endDate) - epochDayFromIso(startDate);
  return days * 1440 + minuteOfDay(endTime) - minuteOfDay(startTime);
}

Install

fune build

With that line in your source, in a TypeScript project (language typescript in fune.project), fune build resolves it and its 1 dependency, pins them in fune.lock, downloads only the TypeScript package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add time.minutes-between

The manifest, vectors and README with only the TypeScript implementation. Install it without the registry with fune add ./time.minutes-between-1.0.0-typescript.fune, or fetch it from a terminal with fune pull time.minutes-between@1.0.0:typescript.

The whole function, every language, is one file too: time.minutes-between-1.0.0.fune, 8,862 bytes, sha256 f28512233b8908b71542c3178abccb2281cb736b93ba1f13ac1eede9c71e9386. It installs into a project of any language.

// fune: before time.minutes-between

// fune: after time.minutes-between

// fune: replace dates.add-days in time.minutes-between

// fune: step time.minutes-between after <n|label>

More from the author

**Local wall-clock time, no time zones.** Both times are read off the same clock on the wall, and the answer is the difference between those readings. It does not know about daylight saving: in the UK, 00:30 to 03:30 on 29 March 2026 is 180 minutes here though only 120 minutes passed, because the clocks went forward at 01:00; on 25 October 2026 the same readings are 180 here and 240 in reality. Payroll and time-and-attendance rules differ on which of those to pay, so this capability does not pick one silently: if real elapsed time matters, convert both instants to UTC with a time zone database first and subtract those.

Times are strictly HH:MM, 24-hour, 00:00 to 23:59. "24:00", "9:00" and "5pm" are errors rather than guesses; the end of a day is 00:00 on the next date.

Files