There is no single word I can think of as an equivalent. It's a way of referring to a time, as a point and not an ongoing thing.
... not terrible at the beginning of the fall of 2014
eg. You were riding a train and at one point went INTO a very long tunnel.
A specific transition point or time, rather than "during" the fall or during the trip through the tunnel, which is a longer event.
Or, the time you went into your house when you go home.
Like, the time you started eating your breakfast yesterday; nothing stops or changes at those times, but the meaning is different to how long you were at home or how long you were eating for.
A point in time.