"at" or "on" before "10.10.2019, 16:30" (JavasScript `toLocaleString` output) [closed]

Let's consider a time format: "10.10.2019, 16:30". I'd like to use it in a sentence. By example, what would be a correct sentence:

• "It started at 10.10.2019, 16:30.",
• "It started on 10.10.2019, 16:30.",

or maybe neither of them?
For me it seem to depend on what the grammar rule is: in this kind of formats (with one or many commas), should the focus be put on the first information presented (date in this case and so "on" shall be used), the last one (time in this example and "at" shall be used then), it depends on the writers intention and context and what is the most important information for him or her or there is no rule about it?

From what I've already found it seems the best option would be: "It started on 10.10.2019 at 16:30", but as it's a generated output of some (toLocaleString) JavaScript function, I'd rather keep this format.

I believe I could also use "Start time: 10.10.2019, 16:30.", but I'm more into not using ":".

Thank You in advance.

In English "on" is generally used for a day

It started on Tuesday

It started on the 23rd of January

whereas "at" is used for times:

It started at 4:30pm

It started at midday on Tuesday

Since you are talking about a time, "at" would be the right choice.

The format you are choosing is not a natural one in English, but since you seem to be dedicated to keeping it, treat it as just an arbitrary specifier of a time, not grammatically different from "4:30pm on Tuesday"