Cute idea... It's a daily calendar that is reused each year and gets better the longer you use it. Each day you write the year and something that happened that day like, "(Child's name) took her first steps." Imagine how neat it would be in 10 years.
Starting January 1st, write good things that happen to you on little pieces of paper: surprise gifts, accomplished goals, the beauty of nature, lol moments, memories worth saving, daily blessings, etc. Then on December 31st open the jar and read all the amazing things that happened to you the past year!