According to the route info a half a day is needed to complete the hike. For good hikers around two hours is needed for the entire hike and for people who hike at a slower pace or like a more lesiurely hike it shouldn't take more than three to four hours depending on how much time you spend on the summit.
First of all, my definition of "day" is the hours of usable sunlight. In the winter, this could be 10-11 hours. Thus to me, a "half day" hike is a hike that takes 4 hours or more.
Round-trip distance for this trail is 8.2 miles. To finish in 2 hours requires hiking faster than 4 mi/hr, which is a brisk pace on flat ground, very brisk on steep terrain.
Many hikers will go no faster than 1-1.5 mi/hr. This implies 5.5-8 hours of total hiking time. In the winter, 8 hours is much more than half a day of usable sunlight.