Addition to time and base 60 numbering

[risedu]

I have column of specified time. E.g. 4859.4 is an input displayed as 48:59.4
When I right click on the cell > format cells… > Numbers tab

Category is number
Format: -12:34.568
Format code text box: 00:00.000

Format code is so I can input time without entering colons ‘:’.

All those times in those specified column, I want to add 5 seconds to them:
=SUM(A2+5.0)

Unfortunately 4859.4 becomes 4864.4. In Microsoft Excel this was not an issue.
How would I get it to display 4904.4, preferably without a complex formula?

[Wanderer]

@risedu

In Microsoft Excel this was not an issue.

Please provide a sample Excel file.
.
In your setup neither Calc nor Excel can know your numbers contain something you will read as time. So I’d like to check, how/if this works.

[PKG]

@risedu

Format code is so I can input time without entering colons ‘:’.

Alternative suggestion:

Tools - AutoCorrect Options - Replace

[Lupp]

@risedu

In Microsoft Excel this was not an issue.

How so? What does MS make of 4859.4+5.0 ?

Also: To format the number 4859.4 as 48:59.4 is an extreme misuse of number formatting. It might be done using the format code
00":"00.0
but, of course, this cannot create a time-value as generally used in spreadsheets which is expressed as a fraction of 1 day.
Generally number formats looking similar to TimeOfDay formats for durations should be avoided. In technical/engineering context durations should always be expressed in a single unit (the s basically). If TOD formats are misused nonenetheless for durations in spreadsheets, the (pseudo-)unit must be the day in the sense of 86400 s, and the hours position must be present.
See also attachment:
disask104379misusingFormats.ods (27.6 KB)