time-units

A tiny, dependency-free TypeScript library for converting between fixed units of elapsed time: milliseconds, seconds, minutes, hours, and days.

The entire implementation is a single TypeScript file: index.ts.

Usage

import {
  HOURS_PER_DAY,
  daysToHours,
  hoursToMinutes,
  millisecondsToSeconds,
  minutesToMilliseconds,
} from "z-time-units";

minutesToMilliseconds(5); // 300_000
millisecondsToSeconds(1_500); // 1.5
daysToHours(2); // 48
hoursToMinutes(1.5); // 90
HOURS_PER_DAY; // 24

API

Constants

Every smaller-per-larger relationship among the supported units:

| Constant | Value | | ------------------------- | ------------ | | MILLISECONDS_PER_SECOND | 1_000 | | MILLISECONDS_PER_MINUTE | 60_000 | | MILLISECONDS_PER_HOUR | 3_600_000 | | MILLISECONDS_PER_DAY | 86_400_000 | | SECONDS_PER_MINUTE | 60 | | SECONDS_PER_HOUR | 3_600 | | SECONDS_PER_DAY | 86_400 | | MINUTES_PER_HOUR | 60 | | MINUTES_PER_DAY | 1_440 | | HOURS_PER_DAY | 24 |

Conversion functions

One function for every ordered pair of distinct units, each with the signature (value: number) => number:

• millisecondsToSeconds
• millisecondsToMinutes
• millisecondsToHours
• millisecondsToDays
• secondsToMilliseconds
• secondsToMinutes
• secondsToHours
• secondsToDays
• minutesToMilliseconds
• minutesToSeconds
• minutesToHours
• minutesToDays
• hoursToMilliseconds
• hoursToSeconds
• hoursToMinutes
• hoursToDays
• daysToMilliseconds
• daysToSeconds
• daysToMinutes
• daysToHours

Each performs a single multiplication or division against one of the constants above. Fractional, negative, and zero values flow through ordinary JavaScript arithmetic:

minutesToSeconds(1.5); // 90
secondsToMinutes(30); // 0.5
daysToHours(-2); // -48

Semantics

• A day is exactly 24 hours. No calendars, timezones, or daylight-saving transitions.
• Values are plain numbers in and out. No validation, coercion, rounding, parsing, or formatting.
• Dates, timestamps, structured durations, and calendar operations belong in higher-level libraries.

Contributing

See the CONTRIBUTING guide for setup and development scripts.

Packaging

Published as ESM-only with bundled type declarations, built into dist/ by npm run build. Runtime-agnostic (browsers, Node, Bun, Deno, workers), with sideEffects: false so bundlers can tree-shake unused exports.

License

MIT — unlike the rest of the surrounding monorepo, which is GPL-3.0-or-later, this package is MIT-licensed to encourage adoption.