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Time Calculator

Date & Time

Add/subtract durations and find time differences

Quick Answer

Time Calculator: Add/subtract durations and find time differences. Convert to seconds: 1 h = 3600 s, 1 min = 60 s, then fold back.

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How to Use

  1. Pick dates or a mode: select start/end dates or switch modes in the Time Calculator.
  2. Instant calculation: results appear immediately with day/week/month equivalents.
  3. Solve both ways: change any field and everything updates — forward or reverse.
  4. Check the context: read the solar-term/holiday/rule notes on this page.

Key Points

  • Time Calculator is a free online date & time tool — open and use, no sign-up.
  • All calculations run locally in your browser; your data never leaves the device.
  • Key capability: Add/subtract durations and find time differences.
  • Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

Time arithmetic

Convert to seconds: 1 h = 3600 s, 1 min = 60 s, then fold back
Time difference: end − start; +24 h when crossing midnight
45 min = 0.75 h (÷60, not ÷100)

FAQ

How do I use the Time Calculator?
Open the page and fill in the input fields — results update automatically. Add/subtract durations and find time differences.
Are the results accurate?
Yes. Standard formulas and conversion factors are used and verified.
Is it free? Do I need to sign up?
Completely free. No registration, login or download required.
Does it work on mobile?
Yes. The responsive design works on phones, tablets and desktops.
Is my data saved?
No. Everything runs locally in your browser.

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Source & Updates

Based on standard calendar arithmetic. Last updated: 2025-07

Authoritative sources:

Last updated:

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Cite this page: YiJianSuan. Time Calculator[EB/OL]. https://www.yijiansuan.com/en/c/date/time-add

Results provided by this tool are for reference only and do not constitute professional advice.