Time Calculator: Add & Subtract Time

Q: Why does time use 60 for minutes and seconds?

Time uses a sexagesimal (base-60) system inherited from ancient Babylonian astronomy. The rule: 60 sec→1 min,60 min→1 hour60 sec 1 min, 60 min 1 hour60 sec→1 min,60 min→1 hour—same logic as clock faces and angular degrees.

Q: How does Expression mode work?

In Expression mode, type durations like 1h 30m + 45s or 2d - 1h 20m. Use d (days), h (hours), m (minutes), s (seconds) with + and −. The parser updates in real time. Handy for quick totals without entering each value separately.

Time	Decimal Hours
15 min	0.25
30 min	0.5
45 min	0.75
1 h 15 m	1.25
2 h 30 m	2.5
6 h	6.0

Time

Decimal Hours

15 min

0.25

30 min

0.5

45 min

0.75

1 h 15 m

1.25

2 h 30 m

2.5

6 h

6.0

Time Arithmetic: Add Hours, Subtract Durations & Date Shifts

Sum or subtract time durations with automatic carry-over. Use row-based input, expression shorthand (e.g., 1h 30m + 45m), or add/subtract from a specific date and time. Payroll, project tracking, and scheduling made simple.

What This Calculator Does

Duration Addition & Subtraction

Enter multiple durations in hours, minutes, seconds. Choose Add (+) or Subtract (−)—the operator sits between rows so it stays clear what it applies to. Results show the total, decimal hours, total minutes, and total seconds. Carry-over is automatic.

Expression Mode

Type shorthand like 2h 15m + 30m or 1d - 5h. Units: d (days), h (hours), m (minutes), s (seconds). The live parser shows how your input is read. Ideal when you already know the total in that format.

Add/Subtract from Date

Pick a start date and time with the datetime picker. Add or subtract days, hours, minutes, and seconds. The result shows the exact date and time—e.g., Wednesday, Feb 18, 2026 at 10:05 PM. A badge shows the day shift when the date changes.

Sexagesimal System

Time runs on base 60, same as clocks and angular degrees. 60 sec = 1 min, 60 min = 1 hour. The calculator handles carry-over internally, so you can enter 65 minutes and get 1h 5m. No mental math needed.

Time Calculator: Add & Subtract Hours, Minutes, Seconds

Add or subtract time durations with automatic carry-over. Row input, expression shorthand (1h 30m + 45m), or date arithmetic. Payroll decimals, project totals, and scheduling. Free, runs locally.

How to Use the Time Calculator

Choose your mode: Duration (add/subtract durations), or Add/Subtract from Date (shift a specific datetime). In Duration mode, use Rows for manual entry or Expression for shorthand like 1h 30m + 45m. In Date mode, pick a start datetime, then enter days, hours, minutes, and seconds to add or subtract. Copy the result with one click.

Sexagesimal System & Carry-Over

Time uses base 60:

60\text{ sec} = 1\text{ min},\quad 60\text{ min} = 1\text{ hour}

. When you add durations, excess units roll up: 65 minutes becomes 1 hour 5 minutes; 90 seconds becomes 1 minute 30 seconds. The calculator normalizes everything internally—you can even enter 2h 65m 90s and get 3h 6m 30s.

Expression Parser

In Expression mode, type units with numbers: d for days, h for hours, m for minutes, s for seconds. Combine with + and −. Examples: 1h 30m + 45m → 2h 15m; 2d - 1h 20m → 1 day, 22 hours, 40 minutes. The parser updates as you type.

Negative Duration & Copy Result

If you subtract a larger duration from a smaller one (e.g., 1 hour minus 2 hours), the calculator shows "Negative Time Difference" and displays the magnitude with a minus sign. Use the Copy Result button to paste the human-readable string (e.g., "3 Hours, 15 Minutes, 0 Seconds" or "Wednesday, Feb 18, 2026 at 10:05 PM") into emails, spreadsheets, or reports.

Time Calculator FAQ

? How do I add two time durations?

In Duration mode, enter hours, minutes, and seconds for each row and choose Add (+). The result shows the summed duration with automatic carry-over—e.g., 65 minutes becomes 1 hour 5 minutes. Or switch to Expression mode and type something like 1h 30m + 45m for instant results.

? What happens when I subtract a larger time from a smaller one?

The calculator displays "Negative Time Difference" and shows the absolute duration with a minus sign (e.g., −1 Hour, 30 Minutes, 15 Seconds). You get both the sign and the magnitude, which helps when tracking overtime or backward counts.

? Why does time use 60 for minutes and seconds?

Time uses a sexagesimal (base-60) system inherited from ancient Babylonian astronomy. The rule:

60\text{ sec} \rightarrow 1\text{ min},\quad 60\text{ min} \rightarrow 1\text{ hour}

—same logic as clock faces and angular degrees.

? Can I add time to a specific date and time?

Yes. Switch to Add/Subtract from Date mode. Pick a start date and time (using the datetime picker), then enter days, hours, minutes, and seconds to add or subtract. The result shows the exact date and time—useful for deadlines, reminders, or scheduling.

? How does Expression mode work?

In Expression mode, type durations like 1h 30m + 45s or 2d - 1h 20m. Use d (days), h (hours), m (minutes), s (seconds) with + and −. The parser updates in real time. Handy for quick totals without entering each value separately.

Time Calculator: Add & Subtract Hours, Minutes, Seconds

Configuration

Information Hub

Time Arithmetic: Add Hours, Subtract Durations & Date Shifts

What This Calculator Does

Duration Addition & Subtraction

Expression Mode

Add/Subtract from Date

Sexagesimal System

Time Calculator: Add & Subtract Hours, Minutes, Seconds

How to Use the Time Calculator

Sexagesimal System & Carry-Over

Expression Parser

Negative Duration & Copy Result

Time Calculator FAQ

? How do I add two time durations?

? What happens when I subtract a larger time from a smaller one?

? Why does time use 60 for minutes and seconds?

? Can I add time to a specific date and time?

? How does Expression mode work?

Time & Date Reference Note