## Explanation

In the Excel date system, one day is equal to 1, so you can think of time as fractional values of 1, as shown in the table below:

Hours | Fraction | Minutes | Seconds | Value | Time |
---|---|---|---|---|---|

1 | 1/24 | 60 | 3600 | 0.04167 | 1:00 |

3 | 3/24 | 180 | 10800 | 0.125 | 3:00 |

6 | 6/24 | 360 | 21600 | 0.25 | 6:00 |

12 | 12/24 | 720 | 43200 | 0.5 | 12:00 |

18 | 18/24 | 1080 | 64800 | 0.75 | 18:00 |

24 | 24/24 | 1440 | 86400 | 1.0 | 21:00 |

Since there are 24 hours in a day, 60 minutes in each hour, and 60 seconds in each minute, you need to divide by 24 * 60 * 60 = 86400 in order to convert decimal seconds to a value that Excel will recognize as time. After dividing by 86400, you can apply a time format of your choice, or use the result in a math operation with other dates or times.

In the example, since B11 contains 43200 (representing 43200 seconds, or a half day) the result is 43200/86400 = 0.5. Once a time format like h:mm or [h]:mm is applied, Excel will display 12:00.

### Displaying a time duration

To display hours that represent a duration longer than 24 hours, minutes in durations longer than 60 minutes, or seconds in durations over 60 seconds, you'll need to adjust the number format by adding square brackets.

```
[h] // for hours greater than 24
[m] // for minutes greater than 60
[s] // for seconds greater than 60
```

The brackets tell to Excel the time is a duration, and not a time of day.

*Note: to use square brackets, you'll need to create and apply a custom number format. Select cells, then go to Format Cells (Control + 1) > Number > Custom.*