Date & Time
Timestamps, timezones, business days, countdowns, and calendar math.
8 tools · all run in your browser
Everything time-related that people search for online, in one place. Convert Unix timestamps to human-readable dates, translate between timezones, count business days across US federal holidays, figure out what day of the week a date fell on, and run countdowns to a future moment.
Two computer-science details that catch most people: Unix timestamps come in seconds (10 digits) and milliseconds (13 digits) — JavaScript uses milliseconds, most Unix command-line tools use seconds, and mixing them up is a common bug. Our Timestamp Converter auto-detects and shows both. Second: dates arithmetic across DST transitions and leap years is genuinely hard; our Date Difference Calculator uses proper calendar-correct math rather than dividing millisecond differences.
For scheduling jobs (cron expressions), setting up countdown timers, or figuring out how many working days remain until a project deadline, pick the specific tool from the list below.
All date & time
- Age at Date CalculatorCalculate how old someone was (or will be) on a specific date. Shows years, months, and days plus totals in weeks and days. Handy for historical timelines and future planning.
- Countdown TimerCount down to any date and time, second by second. Add a label and share the URL — everything lives in the link, no login required.
- Date Difference CalculatorCalculate the number of days between two dates in three modes: total calendar days (with weeks / hours / years-months-days breakdown), working days (weekends excluded, custom holidays optional), or US business days (federal holidays excluded automatically with observed-day shifts).
- Date Duration CalculatorAdd or subtract any combination of years, months, weeks, days, hours, minutes, or seconds from a date. Chain multiple adjustments.
- Date Format ConverterConvert any date into 12+ common formats: ISO 8601, RFC 2822, US MM/DD/YYYY, EU DD/MM/YYYY, Unix timestamps, and human-friendly.
- Time Zone ConverterConvert a time between any IANA time zones. See offsets, live now, and multiple destinations at once. Great for global teams and meeting planning.
- Unix Timestamp ConverterConvert Unix timestamps (seconds or milliseconds) to human-readable dates in every common format. Includes ISO 8601, UTC, relative time, ISO week.
- Weekday FinderFind the day of the week for any date, past or future. Also shows ISO week number, day of year, quarter, and leap-year status.
Frequently asked
The number of seconds since 00:00:00 UTC on January 1, 1970 — the Unix epoch. Some systems (JavaScript, some databases) use milliseconds instead. Our Timestamp Converter auto-detects which one you pasted and shows both.
Use Date Difference in "Business days (US)" mode. It excludes weekends and the 11 US federal holidays automatically (with observed-day shifts). Add company or regional holidays as an extra list.
The international standard for representing dates and times as strings — e.g. 2026-08-19T14:30:00Z. Universally understood by machines, unlike locale-specific formats like "8/19/26" (which means different things in the US and Europe).
For most practical purposes, all three mean the same thing: the time in the Prime Meridian timezone without any DST offset. Z is the shortcut used in ISO 8601 timestamps ("Zulu time" in military parlance).
Multiply by 7/5 (each work week has 7 calendar days but 5 working days). 20 working days ≈ 28 calendar days. Use the Date Difference Calculator for precise per-date math.
Use the Weekday Finder — enter any date and it returns the day of the week. Works for past and future dates using the Gregorian calendar.