We consider our ten year anniversary to be in 2025 but I appreciate the kind words here!
Today is roughly the ten year anniversary of when we publicly announced our intention to launch Let's Encrypt, but next year is the ten year anniversary of when Let's Encrypt actually issued its first certificate:
https://letsencrypt.org/2015/09/14/our-first-cert/
In December of 2015 (~9 years ago today) is was made available to everyone, no invitation needed:
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