Now, I'm not big on the "Whatever Happened, Happened" theory, so I believe this is their present. My friend [Large Tuna815, read his post] has the exact opposite theory to this, so were both posting ours:
When they crashed, discovered the stations, the Others, eventually got off the island, and began to go through time flashes, it was always their present. When in 1954, it didn't happen before. It never happened, or at least not what we think.
In 1977, it never happened before, this was their persent. Now, even though they appeared in the 1977 picture (Namaste), that doesn't mean WHH. Perhaps they changed what the picture was before.
Using my examples, I think that Jughead never went off pre-815. My proof: well the island is still there! Because, in the normal timeline of 1977, there was no Jack with a bomb. It was normal. There was an incident, they make a computer to push a button every 108 minutes. Jack didn't change anything.
Because, (this is my theory), they're not back in time in 1 timeline, they're actually in their present time in another timeline. Confusing, I know.
So, when Sawyer saw Claire giving birth (Little Prince), in the normal timeline he was never there, but in this new timeline he was there.
When Locke saw the hatch light in the jungle while he was banging there, he was never watching in the normal timeline, but in another one. (Little Prince)
Tell me what you guys think :)