Hikers who attempt to hike the entire AT in a continuous outing are known as "through hikers". Walkers who are only doing a portion of the trail are called "section hikers". Hikers are further distinguished by whether they are northbound (NOBO) or southbound (SOBO). Hence, in the parlance of the AT, I am a NOBO section hiker.
Most of the through hikers are NOBO. Large numbers of them leave Springer Mountain in March and April. There is so much competition for shelters, hostels and campsites during this period that hikers are starting earlier and earlier in the year, with the result that they sometimes find themselves walking in snow.
Due to climate and geography a smaller number of through hikers are SOBO. We have met a few of these through hikers as they approach the end of there journey. The average time to complete a through hike is 6 months, but there is a significant variation in the time spent. A few days ago we met a couple of young guys moving quickly down the trail with their walking poles stabbing frenetically. (Interestingly, poles are very popular with the faster walkers.) Although they were moving too quickly to exchange more than a "Hi, how are you?" I later learned they were through hikers on track to finish in about 3 1/2 months. This is an average of about 20 miles per day, a remarkable pace for such a challenging trail.
At the other end of the through hikers spectrum was the relaxed older fellow I met today. In response to my question of how long he had been out he said "All year". (This probably means that he is a "flip-flopper" who has walked all of the trail, but not in a continuous southerly direction.) This walker had the time to chat with me at length, and apparently was trying to enjoy the experience of the AT. Nevertheless, it was clear that he was looking forward to the completion of the hike in about a week's time.