When will Channel 4 reduce its analog signal

Channel 4 (WDIV) has been announcing since last week that "on or around May 15" they will reduce their analog signal, and, one would hope, boost their digital signal. When is this going to happen? It's almost May 20, and the analog signal seems to remain at the same strength. The digital signal, on the other hand, has been extremely droppy of late. After much wrangling, I found a position that works for the digital TV set in my room. For the analog TV set (with converter box) in the living room around noon today, I couldn't find any position that worked for the digital channel, so we fell back to analog. This is all the more annoying because Channel 4 digital reception had been very good for a long time.