How to Use the Duration Calculator

To Calculate Duration Between Two Points:

1. Go to the "Calculate Duration" tab.
2. Enter the "Start Point" date, time, and timezone.
3. Enter the "End Point" date, time, and timezone.
4. Select your "Calculation Mode":
   • Total Duration: Calculates the exact time passed. You can choose to "Count the start day" or "Include the end day" for day-based counts.
   • Business Days: Counts only the days that are not weekends. You can define which days are weekends (e.g., Saturday and Sunday). This mode does not include public holidays.
   • Business Hours: Calculates the total time passed only within the specified "Business Hours Window" on non-weekend days.
5. Click the "Calculate" button.
6. Your results will appear in three formats: a "Summary" (e.g., "2 years, 3 months..."), a "Detailed Breakdown", and "Totalized Units" (e.g., total days, total hours).

To Add or Subtract Time from a Date:

1. Go to the "Add/Subtract Time" tab.
2. Enter the "Start Point" date, time, and timezone.
3. Select whether to "Add" or "Subtract".
4. Enter the duration you wish to add or subtract (e.g., 3 years, 10 days, and 5 hours).
5. Click the "Calculate New Date" button.
6. The resulting date and time will be displayed.

Printing and Copying:

• Click "Print Results" to open your browser's print dialog. Only the results will be printed, not the input fields or buttons.
• Click "Copy" in the results box to copy a summary to your clipboard.

Glossary

DST (Daylight Saving Time)

The practice of advancing clocks (typically by one hour) during warmer months so that darkness falls at a later clock time. This calculator automatically accounts for DST transitions based on the selected IANA timezone, which can sometimes result in 23 or 25-hour days.

IANA Timezone

A standardized name for a timezone, such as "America/New_York" or "Europe/Paris". These names are maintained by the Internet Assigned Numbers Authority (IANA) and represent a region that observes a uniform time, including any DST rules.

ISO 8601

An international standard for representing dates and times (e.g., 2025-10-22T14:30:00-04:00). It provides a clear and unambiguous format, which this calculator uses internally.

UTC (Coordinated Universal Time)

The primary time standard by which the world regulates clocks and time. It is a successor to Greenwich Mean Time (GMT). UTC does not observe Daylight Saving Time. It is often used in aviation, computing, and international coordination.