Although in all of the following sentences we use going, each sentence refers to a different timeA concept which is related to our perception of reality; that part of existence which is measured in seconds, minutes, hours, days, weeks, etc.:

I was going home when the accident happened. (past time)
Who’s that man going over there? (present time)
My brothers are going home this weekend. (future time)

The present participle does not in itself express past, present or future time, but it refers to the same time as expressed by something else in the sentence (was, is, are). We call this "something else" a time markerA verb or auxiliary that marks the reference point of a non-finite form. E.g.: The telephone is known to have been invented by Bell. ("is") He denied being in love with the suspect. ("denied") He must have arrived late. ("must").

However, there are participles that refer to an earlier time than that of the time marker:

Having taken the wrong turn, he ended up in a dangerous suburb. (= After he took/had taken the wrong turn,…)

In this sentence, a perfectThe aspect expressing completion. E.g.: He’s finished university. participle (having taken) is used to refer to a time earlier than that of ended.

Present and perfect participles can also have passive forms:

He was sitting there writing a letter. (writing (and sitting) refers to the time of was)
Having written the letter, he went to the post office. (having written refers to a time earlier than that of went)

The article was still being written when the virus ruined all the computers in the office.
Having been written ten Valentine cards, Geoffrey was clearly the most popular boy in the class.

Diagrams

The aspect of infinitives
The aspect of non-finite forms The aspect of gerunds