Recently, I learned that the NZ mental health project Be Great has designated June 24-30 as Thankfulness Week.
The reasons why are summarised in The Thankfulness Project 2019 page on the Be Great website:

To lift spirits in the coldest darkest week of the year June 24 – 30 is one of the lowest daylight hour weeks in New Zealand, a cold and dark time when people can struggle with depression. The goal is to help people in this time by inspiring them to think of all the good things there are abo...
Published on June 23, 2019 11:30