Triglav can be climbed all year long. The hut bellow the top, Triglavski dom is also a good ski touring goal, so it is a nice tour for skiers also.
Of course there is no via ferata to lead us to the top in winter, it is more a proper winter climb with the slopes up to 50°.
It can be climbed in a day if you are super fit(level 5 on a scale 1-5). Price in that case is 350€ for one person and 500€ for two persons. However I suggest all the guests to take two days to climb it. Price in that case is 550€ for one person and 350€ per person with two or more guests. The hut is open all year long, but the rooms are not heated. Full service in the hut(food, drinks, room) is around 50€ per person.
The climb is done from Krma valley: http://www.triglavguides.com/triglav-climb-from-krma-valley/
Equipment is practically the same as for summer climb, except the clothes should be a bit warmer and you need ice axe and crampons(which are provided by us): http://www.triglavguides.com/equipment-list-for-triglav-climb/