All of (the/a/?) time

I've seen someone type "All of a time" before and I've often used "All of the time".

Should it be:

1. All of the time
2. All of time
3. All of a time
4. <your answer here>

As in:

I make mistakes all of the time.

Solution 1:

"All of the time" is correct, but the more commonly used version is "all the time" (dictionary reference).

"All of time" would be wrong in this context, but "for all of time" can be used to mean forever (as opposed to continually, habitually, or continuously). "All of a time" is just wrong, and I've never heard it.

Solution 2:

Without delving into the details of the actual matches involved, you can get a pretty clear sense of the relatively frequencies of "all of the time" (blue line), "all the time" (red line), and "all of a time" (green line) by looking at this Ngram chart for the years 1980–2008:

To the extent that "all of a time" is used at all, I suspect that it does so through the influence of the not-very-similar phrase "all of a sudden." Here is the corresponding Ngram chart for the alternatives "all of the sudden" (blue line), "all the sudden" (red line), and "all of a sudden" (green line) for the period 1980–2008:

Unmistakably, the dominant phrasings are "all the time" and "all of a sudden." But constantly is far more common than "all the time," and suddenly beats "all of a sudden" all hollow, so you can switch to one of those words if you can't remember which phrase starting with "all" is most popular.