What's the right time of day for plucking buds? When is the best time to harvest buds on a mature plant, morning or evening?

The best time to harvest is in the morning just before the light comes on. In the 1970's experiments were conducted at the University of Mississippi that showed there was a 24-hour cycle of rising and falling levels of THC. In the late '90s Dr. Mahlberg of the University of Indiana showed that THC is produced at the outer surface of the glands. This makes sense, since the THC would be degraded during the day and then restored in the evening on site.