The longest day of the year will be observed Thursday – the summer solstice.

The sun will rise at 5:40 a.m. and set at 8:49 p.m., a total of 15 hours and nine minutes of daylight. The day is also used to raise awareness about Alzheimer’s disease.

Alzheimer’s disease is the most common type of dementia and Don Kline who cares for his wife with the disease in Washington shares why the summer solstice, the longest day of the year, was selected to raise awareness, “As a caregiver you’re going to be care giving the whole day, all day long, day after day. And so, it becomes the longest day, and it’s just a nice way to emphasize that type of thing that’s happening to you because the 21st happens to be the solstice.” Alzheimer’s disease is progressive and impairs memory, language, thought, and eventually the ability to complete daily tasks.

Businesses in Washington have their windows painted purple this week in recognition of the disease and the Alzheimer’s Association encourages people to raise money for research on the longest day of the year.