... So for three years now with approximately 366 days then the block need for 3 years will be 52704 blocks. 808139+52704=860843.
Your math is off, 52704 blocks appear in one year (or so). You could check it yourself 808139-52704=755435, which happened on 24th September last year.
If we set 210000 blocks per four years, then three years would be 157500 blocks. Indeed block 808139-157500=650639 was mined on 2020-09-30.