Learn English – “On the one/other hand” vs. “on the one/other side”

One common tense I error I have noticed has to do with the verb to be. Specifically, students confuse the participles. Thus, one sees, for instance, "was been" or "has being". I have also seen this: "I been..."

Most of the tense errors made by non-native speakers occur frequently with the use of irregular verbs: to be, to have, to go, etc.

One of the most common errors I have encountered is the confusion in constructing the perfect conditional tense of the verb to go. For instance, one might hear "I would have went..." instead of "I would have gone..."

If you allow me to tweak slightly:

I had gone to work at 6 o'clock.

At 6 o'clock, I had gone to work.

Both these are fine if there is a context allowing them, such as:

Yesterday, I returned home at 10 pm and was fast asleep within ten minutes. My day had been very busy - I had risen before dawn, and done my usual 3-mile jog before returning for a shower and breakfast. I had gone to work at 6 o'clock. ...

But the expression indicates the time at which "I" went to work (left home), not some time by which (as you say) I was at work or some way along my way to work. To avoid confusion, choose by.