It's not really that complex, and yes it is standard English. Please don't assume something is slangy or idiomatic because you don't understand it yet. ;)
"We are behind." (ie. behind in your work, or behind schedule)
How far are we behind? (In the sense of time.)
"We are two days behind."
"We were in the doldrums."
How long were we in the doldrums? (Again, asking about time.)
"We were weeks in the doldrums."