# Add Time Calculator

URL: https://speedycalculator.com/calculators/everyday-life/add-time/
Last updated: 2026-10-25

> The add time calculator adds days, hours, minutes and seconds to a date and time, and tells you the resulting date, the clock time in 12- and 24-hour format, and the weekday.

## Inputs

- Start date
- Start time
- Days to add
- Hours to add
- Minutes to add
- Seconds to add

## Results

- Date
- Time
- Time (24-hour)
- Weekday
- Total time added

## Formula

```
Result = start date and time + days + hours ÷ 24 + minutes ÷ 1,440 + seconds ÷ 86,400
```

## Explanation

Adding time across midnight, month ends and leap days is fiddly by hand. Use it to find when a flight lands, a long task finishes or a medication dose is due. Daylight saving changes are not applied – add or subtract an hour yourself if one falls in between.

### How to use the Add Time Calculator

- **Start date**
- **Start time**
- **Days to add**
- **Hours to add**
- **Minutes to add**
- **Seconds to add**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter the start date and time, then the days, hours, minutes and seconds to add.

### Tips

- Check whether the end date should be included – event durations usually include it, elapsed time does not.
- Months have 28–31 days, so "one month" is counted by calendar date, not as 30 days.
- Use 24-hour time or set AM/PM carefully when entering clock times.
- Time zones and daylight-saving changes are not applied unless the calculator says so.

### Common mistakes to avoid

- Counting a 30-day month when a calendar month is meant (or the reverse).
- Forgetting leap years when counting days across February.
- Mixing decimal hours (7.5 h) with clock time (7:30).

### Inputs explained

FieldWhat to enterStart dateA dateStart timeA clock time (hours and minutes)Days to addA numberHours to addA numberMinutes to addA numberSeconds to addA number

### What each result means

- **Date** = floor([Result (days since epoch)] + 0.0000001)
- **Time** = ([Result (days since epoch)] - [Date])×24
- **Time (24-hour)** = ([Result (days since epoch)] - [Date])×24
- **Weekday** = weekday([Date])
- **Total time added** = ([Days to add]×24 + [Hours to add] + [Minutes to add]÷60 + [Seconds to add]÷3600)

## Worked example

Inputs — Start date: 2026-10-25; Start time: 09:00; Days to add: 0; Hours to add: 36; Minutes to add: 45; Seconds to add: 0.

Results — **Date = Mon, October 26, 2026**; Time = 9:45 PM; Time (24-hour) = 21:45; Weekday = Monday; Total time added = 36 h 45 min.

## FAQ

**What time is 36 hours from 9 am?**
9 pm the next day.

**How do I add hours and minutes to a time?**
Add the minutes first, carry each 60 minutes into an hour, then add the hours and carry each 24 hours into a day.

**Does the calculator handle daylight saving time?**
No – adjust by one hour if a clock change falls in the period.

**What formula does the Add Time Calculator use?**
Result = start date and time + days + hours ÷ 24 + minutes ÷ 1,440 + seconds ÷ 86,400.