Unless you purchase a corned beef already prepared (watch the nitrates/nitrites) it takes 2 days.  The carrots, potatoes and cabbage take less than an hour (all depends on size you leave them).

Corned beef is usually poached in liquids on the stovetop at low temperature for a long time.  Then strain the juices and chill (easier to cut the meat when it’s cold).  Cook vegetables in juices next day.  Right before they’re ready add back the sliced beef to heat. You can do it in a crockpot over two days too, that way you don’t need to stay home while it’s taking so long. 

Btw, corned beef without all the preservatives will not be as red but brown.