Uh, now that reminds me of the old jokes about the Intel Pentium floating point division bug. :-)

"Intel inside but it can't divide."

Q&A: THE PENTIUM FDIV BUG

Q: What's another name for the "Intel Inside" sticker they put on
Pentiums?
A1: Warning label.
A2: Truth in advertising.

Q: What do you call a series of FDIV instructions on a Pentium?
A: Successive approximations.

Q: Complete the following word analogy: Add is to Subtract as Multiply
is to
1) Divide
2) ROUND
3) RANDOM
4) On a Pentium, all of the above
A: Number 4.

Q: What algorithm did Intel use in the Pentium's floating point divider?
A: "Life is like a box of chocolates." (Source: F. Gump of Intel)

Q: Why didn't Intel call the Pentium the 586?
A: Because they added 486 and 100 on the first Pentium and got
585.999983605.

Q: According to Intel, the Pentium conforms to the IEEE standards
754 and 854 for floating point arithmetic. If you fly an aircraft
designed using a Pentium, what is the correct pronunciation of
"IEEE"?
A: Aaaaaaaiiiiiiiiieeeeeeeeeeeee!

Q: Why doesn't Quicksort work on a Pentium CPU
A: You can only Conquer, not divide.


But on a more serious note: What you are trying to do should be very easy to code in pretty much any modern language. But if you want to put it online you have to find a way to host it and that can cost a little bit of money. Sadly, I don't know of any already existing solution that works exactly as you described.

Weird indeed ;P

See if this works:

https://jsfiddle.net/hdosb792/

40:30:20.1 + 4:03:02.01 gives 44:33:22.002
There is no place to add more than two / next times.

Is that wrong?

40:30:20.1 is 40:30:20.100, not 40:30:20.001
4:03:02.01 is 4:03:02.010, not 4:03:02.001

So 40:30:20.1 + 4:03:02.01 = 44:33:22.11 (or 44:33:22.110)

Oh I see. But you are not honoring the format. You need to specify all the digits & it will be OK.

This version is more tolerant of the ms formatting:
https://jsfiddle.net/wptL80cz/1/

40:30:20 + 3:02.01 =/= 43:32:21.000

A quick oneliner:

[url=https://tryapl.org/?clear&q=f%E2%86%90100%2060%2060%201000%E2%8B%84i%E2%86%90%7Bf%E2%8A%A5%E2%8A%83%2C%2F(%7B2%E2%8A%83%E2%8E%95VFI%203%E2%86%91%E2%8D%B5%7D%C2%A8%27.%3A%27(%7B~%E2%8D%B5%E2%88%8A%E2%8D%BA%7D%E2%8A%86%E2%8A%A2)%E2%8D%B5%2C%27000%27)%7D%E2%8B%84o%E2%86%90%7B%27%20%27~%E2%8D%A8%2C%E2%8E%95FMT%E2%8D%89(f%E2%8A%A4%E2%8D%B5)%2C%5B0.5%5D%27%3A%3A.%20%27%7D%E2%8B%84o(i%20%2740%3A30%3A20.101%27)%20%2B(i%20%274%3A03%3A02.011%27)&run]https://tryapl.org/?clear&q=f%E2%86%90100%2060%2060%201000%E2%8B%84i%E2%86%90%7Bf%E2%8A%A5%E2%8A%83%2C%2F(%7B2%E2%8A%83%E2%8E%95VFI%203%E2%86%91%E2%8D%B5%7D%C2%A8%27.%3A%27(%7B~%E2%8D%B5%E2%88%8A%E2%8D%BA%7D%E2%8A%86%E2%8A%A2)%E2%8D%B5%2C%27000%27)%7D%E2%8B%84o%E2%86%90%7B%27%20%27~%E2%8D%A8%2C%E2%8E%95FMT%E2%8D%89(f%E2%8A%A4%E2%8D%B5)%2C%5B0.5%5D%27%3A%3A.%20%27%7D%E2%8B%84o(i%20%2740%3A30%3A20.101%27)%20%2B(i%20%274%3A03%3A02.011%27)&run[/url]

Use i to convert input string such as '10:20:30.123' to a number and o to do the opposite. Use normal arithmetic on numbers. Note that output conversion uses modular arithmetic so negative numbers wrap around, in this case to 100 hours (you can change the format if you need more). So o (i '44:33:11.123')-(i '44.33.11.124') gives 99:59:59.999.

Example: o (i '1:0:0.01') + (i '0:59:20.202') gives 1:59:20.212.

It doesn't handle lists but you can use each (¨). All the power of APL is available to you...

For example, to add a bunch of times in one go:

o+/i¨'40:00:00.0' '1:0:0.01' '2:25:59.0' '4:26:0.323'

gives 47:51:59.333.

EDIT: sigh of course gog butchered the url. and looks like you now want formats other than hh:mm:ss.msec? Mm, well, it's bedtime!

Wow. You REALLY don't understand how software works :)

Use HH:MM:SS.mmm like you asked for.

If you want something magical that infers any format you happen to feel like use paper and pencil.

I haven't tried yet if your solution is possible for me to run, but to answer your question - my input times are hh:mm:ss.msec in general, but 0s are often skipped, as in common usage.

Anyway thanks for trying to help, I was looking for already ready solutions and I didn't expect any custom ones. :o

It is really weird that already existing time online calculators have so many faults. With so many video / image / audio online converters / calculators I thought it will be quite simple to find one to fill my need but it seems that this "branch" of online calculators still has a lot of room for improvement. :D

I know how it works AND I knew it will not be a short period of time to create the thing I need.
That's why I asked for ready to use solutions, not to build a page for me. ;)

Then just modify that code to meet you needs. The "hard" part is done. It should take like 5 minutes if you know how it works as you claim. This is trivial stuff.

But I'm done trying to help you. Apparently that's not possible.

Try:
https://datetimecalculator.net/add-time-calculator
https://datetimecalculator.net/subtract-time-calculator

Remarkable help man! I want friends like you.

Why ?, when enemies are generally a lot friendlier... :p