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Hazuu Tools

Time Calculator

Calculate, add, and subtract time values easily.

timerTime Calculator
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Time Between Two Dates

Start Date & Time
End Date & Time
Difference

0s

Total: 0.00 hours

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Add Times

Time 1
Days
Hours
Min
Sec
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Time 2
Days
Hours
Min
Sec
Sum

0s

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Subtract Times

From
Days
Hours
Min
Sec
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Subtract
Days
Hours
Min
Sec
Difference

0s

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Modify Date

Starting Date & Time
Add / Subtract Time
Days
Hours
Min
Sec
New Date

Tuesday, Jun 9, 2026 at 11:45 PM
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About Time Calculator

The Time Calculator is a four-in-one online tool that covers the full range of time arithmetic in a single page. You can find the exact duration between any two date-and-time pairs down to the second, add or subtract two time durations expressed in days, hours, minutes, and seconds, or take a known date and shift it forward or backward by a custom interval to find the resulting date and time.

Typical uses include tracking how long a task actually took versus how long it was scheduled, figuring out a project deadline by adding a known lead time to a start date, calculating billing hours across a shift, or answering simple calendar questions like "what date is 45 days from now at 3 PM?" All four sections update instantly as you type, with no submit button required.

Every calculation runs entirely in your browser. No dates, times, or durations are ever sent to a server, so sensitive project timelines, medical appointments, or personal schedules stay private on your own device. The tool is free, requires no account, and works on any device.

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Key Features

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Four calculation modes in one place

Switch between time-between-dates, add durations, subtract durations, and modify-a-date without leaving the page or opening a second tool.

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Dual output for time spans

The time-between section shows both a broken-down result (e.g., 2d 3h 45m 10s) and a total-hours figure (e.g., 51.75 hours), so you can copy whichever format your timesheet or invoice expects.

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Days, hours, minutes, and seconds

All duration inputs accept four separate fields, so you can work at any precision — from a quick "3 hours" to a precise "1d 4h 23m 55s" — without converting units first.

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Date-shift with add or subtract toggle

The Modify Date section lets you pick a base date and time, choose whether to add or subtract, enter the offset in any combination of days through seconds, and instantly read the resulting calendar date and time of day.

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Instant live results

Every section recalculates as you change any field. There is no submit button to press, which makes iterative adjustments — like testing different shift lengths or lead times — fast and natural.

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Client-side only, no data leaves your browser

All arithmetic is performed in JavaScript on your own device. Dates and durations you enter are never transmitted, stored, or logged anywhere.

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How to Use

01

Choose a Mode

Select from four calculation types: time between dates, add times, subtract times, or modify a date.

02

Enter Values

Fill in the required dates, times, or duration fields for your chosen calculation.

03

View Results

Results are calculated and displayed instantly as you type. No need to click a button.

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Example

Enter a start and end date-time to see the duration broken down into days, hours, minutes, and seconds, plus the equivalent total hours — useful for timesheets or project tracking.

Start → End
Start: 2025-03-10 09:00
End:   2025-03-12 13:45
Duration result
2d 4h 45m 0s
Total: 52.75 hours
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Common Use Cases

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    Calculating billable hours across a shift or project

    Enter the exact start and end date-time of a work session to get both a broken-down duration and a decimal hours total ready to copy into a timesheet or invoice. Unlike a plain hours calculator, this also handles sessions that span midnight or multiple days.

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    Finding a future deadline from a lead time

    Use the Modify Date section to add a known lead time — for example, 14 days 6 hours — to a project start date and see the precise deadline, including the day of the week. This is different from a date-only calculator because you can specify hours and minutes as part of the offset.

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    Summing up multiple logged durations

    Add two time blocks together — such as 2h 45m plus 1h 30m — to get a combined total without doing mental arithmetic or converting everything to minutes. Useful for consolidating fragmented work logs or travel time segments.

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    Checking how much time remains until an event

    Set today as the start and your event date as the end to get the countdown broken down by days, hours, and minutes. Because the result also shows total hours, you can see at a glance whether you have more or fewer than, say, 48 hours left.

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    Adjusting scheduled times for time zone offsets or delays

    Use the Subtract Times section to deduct a known delay or offset from a planned duration, or use Modify Date to back-calculate when to start a task if it must finish by a specific time.

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Frequently Asked Questions

What is a Time Calculator? expand_more
A Time Calculator is an online tool that performs various time-related operations including finding the difference between two dates, adding or subtracting durations, and modifying dates by specified time intervals.
How do I calculate time between two dates? expand_more
Enter a start date and time, then enter an end date and time. The calculator will instantly show the difference in days, hours, and minutes, plus the total number of hours.
Can I add days, hours, minutes, and seconds together? expand_more
Yes. Use the Add Times section to enter two time durations with days, hours, minutes, and seconds. The calculator sums them and shows the total in a normalized format.
Is this tool free and private? expand_more
Yes. The Time Calculator is completely free to use and all calculations happen locally in your browser. No data is sent to any server.
How is this different from the Hour Calculator? expand_more
The Hour Calculator focuses on summing work-shift hours to produce a total — it is designed for payroll and timesheet use. This Time Calculator covers four distinct modes: finding the span between two date-times, adding or subtracting arbitrary durations in days through seconds, and shifting a specific date forward or backward. Use the Hour Calculator when you need to total up daily work hours; use this tool when you need any of the broader time-arithmetic operations.
How is this different from the Date Calculator or Days Calculator? expand_more
The Date Calculator and Days Calculator typically show the number of calendar days between two dates. This Time Calculator goes further: it works at second-level precision, provides both a broken-down (Xd Yh Zm Ws) result and a decimal total-hours figure, and also lets you add or subtract durations and compute a resulting date-and-time — not just a day count.
What does the Modify Date section do? expand_more
Modify Date lets you start with any date and time, then add or subtract a custom offset expressed in days, hours, minutes, and seconds. The output is the resulting calendar date and time, shown as a full readable string including the day of the week. For example, adding 45 days and 6 hours to March 10 at 9:00 AM gives you April 24 at 3:00 PM.
Can the time difference be negative? expand_more
Yes. If the end date-time is earlier than the start date-time, the difference is shown with a minus sign. Similarly, subtracting a larger duration from a smaller one in the Subtract Times section returns a negative result.
Does the tool account for daylight saving time? expand_more
The calculator uses your browser's local Date object, which respects your device's time zone and DST rules when parsing dates. If both dates are in the same DST regime the result is exact; if they cross a DST boundary the browser adjusts the offset automatically, so the output reflects real elapsed clock time.