Hiking / Snowshoeing / Skiing to Kjerag in winter is dangerous and should not be taken lightly.
The access roads to Kjerag are closed in winter. This makes it impossible to start at the summer trailhead, and therefore, Kjerag cannot be reached within 1 day. Kjerag has an arctic climate and is covered in meters with snow from as early as November, until as late as May. There is a snow avalanche risk along the summer trail. In addition, the weather is often very harsh, with snow/fog/low visibility, high winds, and temperatures down to minus 20 below freezing. Conditions change fast.
By far most, even experienced hikers, will not be able to hike Kjerag in winter. You really need proper planning, equipment, and local guides. Please take the safety of yourself and others into consideration.