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 500€ for one person and 300€ per person for two persons. However I suggest all the guests to take two days to climb it. Price in that case is 800€ for one person and 425€ 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 80€ per person.
The climb is done from Krma valley: https://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): https://www.triglavguides.com/equipment-list-for-triglav-climb/
If you need more information about climbing Mt. Triglav during the winter, I recommend reading this article I published in collaboration with Explore-Share: ‘Climbing Mount Triglav in Winter: A Definitive Guide to Ascent in the Off-Season.’ You can find it at https://www.explore-share.com/blog/climbing-mount-triglav-winter-definitive-guide-ascent-off-season/.