Probably since the first time that a human saw or heard an owl there has been a fascination with this bird of prey. With early humans that curiosity began to translate into omen type meanings that still are with many cultures in today's societies. Some of those first humans may have encountered an owl at a time when they were seeking something. They may have felt that the presence of an owl brought them wisdom in finding an answer or an item and then saw the owl as a good omen and a bringer of wisdom.
If a death occurred at night and the hooting of an owl came just before that death, those early humans might have felt that the owl was what brought on the demise of the individual. Those humans would have looked at the owl as a bad omen and a possible harbinger of death.
As we humans have grown in our understanding of animals, some of us just think this majestic of nocturnal birds is just a magnificent specimen of life. We find their plumage and body shapes to be most appealing along with their habits of survival fascinating.
Owls have become a popular bird due to movies like Harry Potter and others that featured the owl in a form of wisdom or wizardry, too.
No matter what your reason for loving owls is, one can hardly deny the incredible and sometimes spooky nature of the owl.
It's no wonder owl planners and calendars are so popular.