Date & Time
Calendar and time tools for dates, durations, weekdays, and planning.
Explore 10 free date & time tools, including Add / Subtract Days Calculator, Business Days Calculator, Countdown Timer, Date Difference Calculator, and more.
Choose the right tool
Decide whether your question concerns calendar dates, elapsed time, working days, or an instant in a time zone. These are different tasks. A calendar day can contain 23 or 25 hours when daylight saving time changes, and a weekday is not necessarily a working day if a holiday falls on it. Choose the tool after deciding what counts toward your result.
- Date Difference Calculator: Compare calendar dates when you need a date-based interval.
- Business Days Calculator: Count working days with the weekend and holiday rules exposed by the tool.
- Time Zone Converter: Compare local clock times for a dated event across named zones.
- Unix Timestamp Converter: Inspect a machine timestamp and check whether its unit is seconds or milliseconds.
Showing all 10 tools.
Add / Subtract Days Calculator
Calculate a date before or after a chosen number of days, weeks, months, or years.
Business Days Calculator
Add business days from today or count weekdays between dates with US federal and custom holidays.
Countdown Timer
Start, pause, reset, and use quick countdown presets in your browser.
Date Difference Calculator
PopularFind exact years, months, elapsed days, inclusive days, weeks, weekdays, and weekends between two dates.
ISO 8601 Converter
Parse and create ISO 8601 date/time values.
Time Duration Calculator
Find hours, minutes, total minutes, and decimal hours between times.
Time Zone Converter
PopularConvert meeting times between cities and IANA time zones with DST-aware offsets.
Unix Timestamp Converter
PopularConvert Unix seconds, milliseconds, ISO dates, UTC, and local time.
UTC to Local Time Converter
Convert UTC into local time with offsets and ISO output.
Week Number Calculator
Calculate ISO week numbers and week-years.
Worked example: count a week correctly
- From Monday 14 September 2026 to Monday 21 September 2026, the ordinary date difference is seven calendar days.
- If both endpoints count, that interval contains eight calendar dates. State the endpoint rule when sharing a deadline or attendance count.
- Counting weekdays with the start excluded and the end included gives five weekdays before any holidays are removed. For an actual deadline, check the applicable holiday calendar and cutoff time separately.
Common mistakes to avoid
- A numeric date such as 03/04/2026 is ambiguous. Prefer an explicit month name or YYYY-MM-DD when exchanging dates.
- A UTC offset is not a time-zone rule. Use the event date and a named zone for scheduling, especially across daylight saving transitions.