SEDE doesn't give the consecutive days on a user, so no luck there.
We can do an educated guess though: the user with the highest number of consecutive days is probably a very active user, so what if we just check how many consecutive days a post was created?
This is how far I got using SEDE:
select OwnerUserId [User Link]
, CreationDate
, days_between_posts
, RW=ROW_NUMBER() OVER( PARTITION BY GRP ORDER BY OwnerUserId, CreationDate)
from ( select OwnerUserId
, CreationDate
, datediff(d, lag(CreationDate) over (order by OwnerUserId, CreationDate), CreationDate) days_between_posts
, DATEDIFF(d, '1900-01-01' , CreationDate)- ROW_NUMBER() OVER(partition by OwnerUserId ORDER BY CreationDate ) AS GRP
from ( select OwnerUserId
, cast(CreationDate as date) CreationDate
from Posts p
where OwnerUserId > 1
group
by OwnerUserId
, cast(CreationDate as date)
) p
group
by OwnerUserId
, CreationDate
) cd
where 1=1
order
by OwnerUserId
, CreationDate
I had problems grouping the data together on the user, not sure why the results got invalid... Still working on it. Since we only get 50.000 rows now, we can't say who won...
On Stack Overflow, VonC seems to do a good job, but no status update since 2015.
DaysSinceStackOverflowInception - 1
.