>How do you write the time? Do you put seconds or minutes before hours? Why not?

No, because the seconds are rarely important.

>How do you write the year? Do you put decade before century?

No, because that's not how numbers work.

>How do you write numbers? Do you put the ones place before the tens?

Same answer.

>Toddmorey asked why units don’t go from small to large and I explained that it is inconsistent with how we write numbers.

Dates aren't numbers. There is a lot more context and meaning around dates that we need to consider when we verbalise and write them. But, for the purposes of e.g. data storage then absolutely - we can consider them no different from numbers. You have to understand that isn't the case with conversational English, though.