It all depends on the kind of armour. If it's akin to full plate, forget it. The quicker variants only take about half an hour IIRC.<br/>If it's more like a  chainmail or lamellar, quite fast, as long as you have someone to help you and are already wearing the undergarments  (mandatory with chain). There might be leather belts to fasten, for example.<br/><br/>I've seen a guy donning a chain by himself in less than 30 seconds, but that cost him some pain.