Let's say I want to calculate my overtime in Google Spreadsheets. I need the function to either convert an integer (10) to a duration (10:00:00), or vice versa, to be able to perform a calculation.

So,

```
=A1 - 8
```

or

```
=A1 - 8:00:00
```

should be converted to

```
10:30:00 - 8:00:00
```

and return

```
02:30:00
```

in order to continue the calculation in another cell.

`=A1-1/3`

with custom format of`[hh]:mm:ss`

. – pnuts`1/3`

... thanks in advance! – Levano