A nifty thrifty website is whencanIreusethiscalendar.com.
Because of it we were able to reuse this lovely thing again this year after a mere six year wait.
Marie Kondo might not approve of that kind of saving, but she will be even more disapproving of the length of time we will have to hang on to it for a third time use. 2019 calendars do not sync up with the yearly dates again until 2030.
Your 2018 calendar is usable again in 2029. Not bad.
If you are a first wave baby boomer you might as well give your 2020 calendar to a millennial packrat right now unless you plan on taking really good care of yourself so you can use it again in 2048.
Have a good year!