Windows 10 Mobile 1607, the Anniversary Update, was meant to go out of support a few days ago, but yesterday Microsoft updated their documentation to add another year to their support agreement.
This means the OS, released in August 2016, will continue to receive security and non-security updates until the October 9, 2019 , and users will still be able to contact Microsoft for assistance and support.
This is the second time Microsoft has extended support for the OS, the last time by 6 months in April 2018
Interesting they keep extending this date.