The ones I've tried out for possible future purchase have been all but impossible to use during the day. I wasn't told of any direct limitations, but I'd imagine it would be downright damaging to use them even in semi-bright daylight. I'm not military so I don't know if they use different ones or different tech even, but I think these were made by Bushnell.
Keep in mind, though, that according to the Tom Clancy universe, goggles can be readily switched between EM, NV and Thermal imaging. And that they apparently work best when they glow.