Ok... two different items here....
The difference between a UV lamp, and a standard flood lamp, is the type of light produced. Specifically, a UV fixture creates UV light (Ultra Violet). This is rather like asking whats the difference between a red bulb, and a yellow bulb -- they simply produce a different spectrum of light. UV is used in sterilizing medical equipment, and to cure adhesives, among other uses.
I've worked with UV adhesives - what you are describing does NOT sound like any UV adhesive Ive used (and I've used several kinds of adhesives, including RF, urethanes, catalyst based, cyano-acrylics, PVA... the list goes on....)
If the labels you were using were actually cured by UV light, you'd have noticed them setting much faster than the 'several hours' you mention. It's more likely that the labels are hardening simply because the sunlight is providing a little additional warmth, which is causing the glue to harden faster (most common glues work by evaporation - the water dries out of them, causing the glue to harden). If this is what is happening, you could achieve the same results using a flood light bulb (which produces a bit of heat during normal operation), or other mild heat source - like your hair dryer, or possibly a heating pad.
By the way, UV adhesives will NOT cure, without a source of UV.
Your best bet is to contact the manufacturer of the label, to see their recommendations, or to switch the label adhesive to a faster setting version. UV, and RF glues, for example, are made which cure in seconds..... not hours... and are in wide use in furniture making, as one example.
We can't really give anything more specific, without more details on the labels, and product they are being applied to.
Good Luck