The weird thing is that the city has a 30 hour day length, but the Neighborhood has a 30.23 hour day length. I assume the hood day length is for the globe clock.
So the time of the clock in neighborhoods wouldn't line up with the timing for the algae glow unless the city were updated to 30.23 (which I assume is a more correct value than the unused exactly-30).
Then again, this is a living thing not a celestial body. Since the lake was dormant for a long time, it might be logical to think it wouldn't go right back to having the exact same cycle length as the clocks were first based on.