No. They have Tritium vials under the fiber optics. So, they glow all the time. You just won't notice it in the day time.
I thought the tfo glow in day. What sights glow in night and day ??
They do, they "glow" in the under daylight or artificial light by transmitting that light through light tubes, they also have a tritium dot that glows under it's own power all the time but you would only see that in the dark as it's overpowered by other light sources.
No source, but the TFOs have to be manufactured after June, 2013 to fit the Shield properly. Truglo revised the sight for the Shield at that time, earlier manufactured dates are too wide for the Shield slide. I know some have used them anyway, but they do hang over a little. I'm trying to find a set made after June to put on my Shield, but haven't found any yet.