1. Export the data into CSV from the historical chart
2. Change the date to an index starting at 0
3. copy into https://www.graphpad.com/quickcalcs/linear2/
4. Copy formula into desmos (replace “X” with “x”)
5. Add x*0 + 50 and x*0 to find the points where 50% and 0% are reached
6. Use datetime calculator and just add the number of months to 2009-01-01

There’s probably a better tool, but a 5 minute search didn’t find one for me 🤷