If I recall correctly, there were people from PST and farther west, as well people in Australia/NZ, where this problem occured on Leap Day.

Lab caches are logged with UTC date, which would make sense if McTigueTowne's labs are being counted fot the next day (PST is -7, so any log after 5 pm PST results in a new day)

Lab caches can ruin milestone stats as well due to this problem. They only "match" your log order, if you are in a +/-0 timezone to UTC.