Thanks guys! I understand the problem now, I mistakenly looked at the date reading in the inner and outer loops when you did in fact state it was a consequence of the clock advancing between the two checks on the same line. I'll edit as suggested by both of you, read the hour once and use it twice a...

I see what you are saying and I agree it could cause a picture to be uploaded outside the permitted time but surely it could only happen if the inner loop was already executing, in other words immediately after 21:00. This is a slightly different scenario, it actually executes the inner loop once at...

This one has me mystified, all I can think of is the relatively slow speed of the Pi B is causing some kind of race condition. It's a simple script that is supposed to run and annotate a picture from the Pi's camera and upload it to a web site but only between certain times. It works fine except tha...