Placement is a huge factor in bloom time. Needs at least 6 hours of sun, but if placed so it falls into shadows mid-late afternoon, will bloom earlier in the day than an identical plant that's in the sun until it sets. I try to put these on the east side of the house, morning glories on the west side (so they get direct sun as late as possible, causing the blooms to stay open longer in the morning, the same effect but opposite manifestation of it.)