Measure calendar dates
Calculate age to today, a signed gap between two dates, or a configurable working-day count.
Best when the question is about dates on a calendar; decide whether endpoints and non-working days count.
Date & Time
Calculate age, date gaps, workdays, hours, countdowns, and time zones.
Choose the calendar, work-time, or time-zone question first, then use a focused tool with its counting rules and limits kept visible.
- Calculations run in this tab
- Counting rules kept visible
- DST and clock limits explained
Decision guide
Start with the kind of time you need to measure
Calendar spans, work records, and time-zone conversions use different rules. These three complete paths cover all six tools without leaving an empty grid position.
Track work and deadlines
Total clock-in and clock-out records or watch the remaining time to a local target.
Best for wall-clock inputs; confirm overnight, break, overtime, device-clock, and target-zone assumptions.
Coordinate named time zones
Interpret a wall-clock time in one named zone and compare the same instant across other zones.
Best for meetings and launches; selected dates matter because DST can change an offset or repeat or skip a local time.
Tool directory
Date & Time tools
Showing 6 of 6 tools
Timezone Converter
Enter a wall-clock time in a named source zone to compare the same instant across browser-supported IANA zones, with DST warnings and meeting overlap.
Popular Trending
Age Calculator
Enter a birth date to calculate calendar age to today in years, months, and days, plus a next-birthday and elapsed-day summary.
Popular
Date Difference Calculator
Enter two dates to see the signed, exclusive gap in total days, whole weeks, and hours; use Business Days when non-working days must be excluded.
Popular
Business Days Calculator
Enter a date range, choose which endpoints and weekend days count, and optionally load a holiday CSV to calculate working days.
Popular
Countdown Timer
Enter a target in the browser's local date and time to watch remaining days, hours, minutes, and seconds using the device clock.
Work Hours & Time Card Calculator
Enter clock-in and clock-out times plus paid or unpaid breaks to total shifts and weeks, with overnight support and optional user-set overtime and rounding.
Practical category guide
Choose the counting rule before trusting the number
These six tools answer different kinds of date and time questions: Age Calculator measures calendar age to the viewer's current local date; Date Difference Calculator reports the signed, exclusive gap between two plain dates; Business Days Calculator applies an explicit endpoint rule, weekend pattern, and optional user-supplied holiday list; Work Hours & Time Card Calculator totals wall-clock shifts and breaks; Countdown Timer tracks a local target against the device clock; and Timezone Converter interprets a wall-clock time in a named source zone before showing the same instant elsewhere. Leap years, varying month lengths, inclusive versus exclusive ranges, overnight shifts, daylight-saving transitions, and holiday rules can all change a result. Choose the convention first, then use the output in the calendar, policy, contract, or schedule that governs the task.
Before calculating, decide whether you mean calendar units, elapsed time, working days, wall-clock hours, or one instant viewed in another zone. Those are different questions and can correctly produce different answers.
What the Date & Time tools help with
Separate calendar age from elapsed time
Age Calculator uses calendar anniversaries to report years, months and days to today; Date Difference Calculator reports a signed exclusive gap in total days, whole weeks and hours.
Make the working-day rule explicit
Business Days Calculator lets you choose which endpoints count, select a weekend pattern, and supply the holiday dates that actually apply.
Coordinate named time zones
Timezone Converter applies the browser's IANA rules for a selected date and warns when daylight saving makes a local time repeated or nonexistent.
Track wall-clock work and targets
Work Hours & Time Card Calculator totals shifts and breaks; Countdown Timer displays time remaining to a local target using the device clock.
Selection guide
Which date or time tool should I use?
Match the question to the output, then read the rule in the final column. It explains the boundary that most often causes an off-by-one day, a shifted meeting, or an incorrect work total.
- Measuring a span of time?
- Use the Age Calculator for a birth date and the Date Difference Calculator for any two dates.
- Coordinating across regions?
- The Timezone Converter aligns a single moment across multiple time zones.
- Counting toward a deadline?
- The Business Days Calculator counts working days and the Countdown Timer tracks the time left to an event.
Calculate age to today
Age Calculator
- Inputs
- Birth date
- Output
- Calendar age in years, months and days; next-birthday and elapsed-day summaries
- Rule to check
- Today comes from the viewer's local calendar. A 29 February anniversary is treated as 1 March in common years.
Measure two dates
Date Difference Calculator
- Inputs
- Start date and end date
- Output
- Signed total days, whole weeks and hours
- Rule to check
- The result is the exclusive date subtraction. Reverse inputs produce negative values; use Business Days for non-working-day exclusions.
Count working days
Business Days Calculator
- Inputs
- Date range, endpoint rule, weekend preset, optional holiday CSV
- Output
- Business, calendar, weekend and supplied-holiday counts
- Rule to check
- No public-holiday list is inferred. Half-days and regional rules require your own source and interpretation.
Total shifts or a week
Work Hours & Time Card Calculator
- Inputs
- Clock-in/out times, paid or unpaid breaks, optional rounding and overtime thresholds
- Output
- Gross, break, net, regular, overtime and decimal-hour totals
- Rule to check
- Overtime is arithmetic from user-set thresholds, not a legal determination. Wall-clock shifts do not adjust for DST.
Count down to a target
Countdown Timer
- Inputs
- Target date and time
- Output
- Live remaining days, hours, minutes and seconds
- Rule to check
- The zone is the browser's local zone, the device clock is the time source, and unfinished targets are not restored after reopening.
Compare regional times
Timezone Converter
- Inputs
- Wall-clock date/time, named source zone, one or more destination zones
- Output
- The same instant in each zone, offsets, DST warnings and a working-hours overlap grid
- Rule to check
- Rules come from the browser's IANA data. Repeated times choose the earlier occurrence; skipped times are flagged.
Practical workflows
Combine tools without mixing their counting rules
Each workflow keeps calendar dates, working-day rules, wall-clock time, and named time zones explicit from start to finish.
- Find an exact age in years, months and days with the Age Calculator.
- Count the days between two dates for a project timeline using the Date Difference Calculator.
- Convert a meeting time across cities with the Timezone Converter before you send an invite.
- Calculate a deadline that skips weekends using the Business Days Calculator.
Start here
Build a project deadline
Separate total calendar time from the working days the team can actually use.
- 01Measure the signed calendar gap with Date Difference Calculator.
- 02Choose the endpoint and weekend rules in Business Days Calculator.
- 03Load the project or regional holiday list instead of assuming one.
- 04Add a local Countdown Timer only after the target date, time, and zone are agreed.
02
Calculate an age
Use a birth date for calendar age rather than dividing elapsed days by 365.
- 1Enter the birth date and confirm today's date on the device.
- 2Read years, months, and days as a calendar breakdown.
- 3Treat total hours as whole calendar days multiplied by 24, not a precise lived duration across DST.
03
Coordinate an international meeting
Anchor the meeting to a named source zone so seasonal offset changes stay attached to a real date.
- 1Enter the proposed wall-clock time in the source participant's named zone.
- 2Add destination zones and review date rollovers, DST alerts, and the overlap grid.
- 3Send the final invite with the zone name and verify recurring dates separately.
04
Prepare a weekly time card
Record the shift facts first; apply company or legal rules only after confirming the correct policy.
- 1Enter clock-in, clock-out, and paid or unpaid breaks for each shift.
- 2Review overnight handling and any rounding settings before totaling the week.
- 3Set overtime thresholds only when the governing policy is known, then export or print the result.
05
Count down to an event
Use the timer for a target already agreed in the viewer's local zone, not for resolving a zone ambiguity.
- 1Convert an externally announced time to the viewer's zone first when necessary.
- 2Enter the local target and confirm the date, clock time, and device clock.
- 3Keep the page open while using the live display; the unfinished target is not saved for a later visit.
Before you calculate
A quick rule and input checklist
Name the counting convention
State whether a date range includes the start, the end, both, or neither before sharing the result.
Use ISO-style date fields
The tools use browser date inputs and plain YYYY-MM-DD values, avoiding ambiguous typed forms such as 03/04/2026.
Supply the right non-working days
Choose the correct weekend pattern and load the holidays that apply to the organisation, location, and period.
Attach a zone to a wall-clock time
For cross-region events, record a named zone such as Europe/London rather than only an abbreviation or a fixed offset.
Confirm the clock and policy
A live timer depends on the device clock; work totals depend on the break, rounding, and overtime rules you choose.
Terms that are easy to mix up
Four distinctions worth checking
- Calendar difference and elapsed duration
- Calendar difference counts human date units such as years and months. Elapsed duration measures a fixed quantity such as total days or hours.
- Inclusive and exclusive range
- An inclusive range counts an endpoint; an exclusive range omits it. Two valid conventions can differ by one or two days.
- Time zone and UTC offset
- A time zone is a set of dated civil-time rules. An offset is only the zone's difference from UTC at one particular instant.
- Ambiguous and nonexistent local time
- When clocks move back, one wall time can occur twice; when they move forward, another local time can be skipped entirely.
What these tools cannot know automatically
They cannot infer which contractual endpoint counts, your organisation's holiday calendar, local overtime law, a payroll policy, the intended zone of a zone-less countdown, or whether a future government time-zone rule will change. Choose those rules explicitly and confirm important schedules in the calendar, contract, or policy that governs them.
Help