Probably quite a separate phenomenon, but if I wake when it's still night and I want to know what time it is, I'll often blink my eyes open for a tiny fraction

Probably quite a separate phenomenon, but if I wake when it's still night and I want to know what time it is, I'll often blink my eyes open for a tiny fraction of a second to see the glowing alarm clock. I often don't know what time it is until I "read" the time from my memory. (It's either my memory or the after-image on my retina.)