Can I use the duration calculator for time spans that cross midnight?

Yes. Enter the start time and end time on different days. The calculator adds the necessary hours to account for the day boundary. For example, 10:00 PM to 2:00 AM returns 4 hours.

Does the calculator handle months and years in the result?

It shows the span in days, hours, minutes, and seconds. Months and years are not used because their length varies. A 30-day span could be one month (June) or one month minus one day (February to March).

What happens if I enter times in different time zones?

The duration calculator does not convert time zones. It treats each time as entered. Use the Time Zone Converter to convert both times to the same zone first, then enter them.

Why does a span that includes a DST change show 23 or 25 hours?

On the spring-forward day, clocks jump from 2:00 AM to 3:00 AM. The day has only 23 hours. On the fall-back day, clocks go from 2:00 AM back to 1:00 AM. The day has 25 hours. The calculator uses the IANA time zone database to apply the correct offset for each transition.

How do I calculate the duration between two dates in different years?

Enter the full dates: month, day, and year. The calculator handles year boundaries, leap years (February 29 in 2024, 2028, and so on), and century rules. A span from December 31, 2023, to January 2, 2024, returns 2 days.

Is the result the same as what I would get in Excel?

Excel's `DATEDIF` and `TEXT(end-start,"h:mm")` functions work differently. Excel counts calendar days, not full 24-hour periods. For time-only spans, Excel's decimal representation (0.5 = 12 hours) requires manual conversion. The duration calculator gives results in plain units without extra steps.

Duration Calculator

How the duration calculator works

You enter two points: 9:15 AM to 5:30 PM, or July 4 at 10:00 AM to July 7 at 2:00 PM. The tool handles the arithmetic that manual subtraction gets wrong. Some days have 23 hours. Some have 25. A month is not always 30 days.

Results appear in multiple units at once. Days, hours, minutes, seconds. No converting. DST transition days are handled correctly. That is where most manual calculations fall apart.

How many hours and minutes passed?

For a same-day span like 9:15 AM to 5:30 PM, enter both times and pick "same day." The calculator subtracts the start from the end.

Why this goes wrong manually: you cannot subtract 15 from 30 directly if you borrow from the hour incorrectly. The correct answer is 8 hours and 15 minutes. The calculator does the borrowing for you.

For spans that cross midnight (11:00 PM to 2:30 AM), the tool adds 24 hours to the end time before subtracting. Manual methods often return a negative number or force you to remember the midnight rule.

How many days passed?

For date-only spans, enter the start date and end date. The calculator counts the number of full 24-hour periods separating them.

The common mistake: counting both the start date and the end date. Start a project on March 10 and finish on March 12. The elapsed time is 2 days, not 3. Most duration calculators follow this rule. The difference equals the number of full 24-hour periods between the two points.

Including or excluding the end date

This setting trips up most users. The calculator offers a toggle: include end date or exclude end date.

Include end date counts the start and end days. Use this for age calculation. Someone born on January 1, 2000, turns 1 on January 1, 2001. That is one day, including both the birth date and the birthday.

Exclude end date counts only full periods between. Use this for deadlines. A report due Friday at 5:00 PM, submitted Monday at 9:00 AM, gives an elapsed time of 2 days and 16 hours (Friday 5 PM to Monday 9 AM, excluding the end moment).

The Days Between Dates FAQ has more on when to use each setting.

Age, countdowns, deadlines

Age calculation: Enter birth date and today's date. Include the end date. The Age Calculator FAQ explains why this method matches how birthdays work.

Countdowns to events: Enter today as the start and the event date as the end. Exclude the end date. A wedding on December 31 shows how many full days remain, not counting the wedding day itself.

Deadlines and project timelines: Enter the start of work and the deadline. Exclude the end date. The tool shows exactly how much time you have, down to the second.

DST transition days: The calculator handles these automatically. In the US and Canada, clocks spring forward on the second Sunday in March. That day has 23 hours. On the fall-back day (first Sunday in November), the day has 25 hours. The Elapsed Time Calculation FAQ shows examples of how this affects duration.

Understanding the results format

The calculator returns results in several formats. Pick the one you need.

Unit	Example for a 2-day, 5-hour, 30-minute span
Days	2.23 days
Hours	53.5 hours
Minutes	3,210 minutes
Seconds	192,600 seconds
Full breakdown	2 days, 5 hours, 30 minutes, 0 seconds

The decimal hours conversion (useful for payroll) uses the standard: minutes divided by 60. Fifteen minutes equals 0.25 hours. Thirty minutes equals 0.50 hours. Forty-five minutes equals 0.75 hours.

Quick reference for decimal hours:

Minutes	Decimal hours
5 min	0.08
10 min	0.17
15 min	0.25
20 min	0.33
30 min	0.50
45 min	0.75
55 min	0.92

Keep this table handy for timesheet entries. The Billable Hours Guide has the full 60-minute breakdown.