I got mine at about 00:10 UTC on the second day of Winter Bash. The first day I went on a rampage on Stack Overflow and flagged / downvoted a lot of non-answers and low quality posts and managed to rack up 130 votes for the day. As Glorfindel mentioned you get the votes back once a post is deleted and if I'd been a bit more determined I could have probably got 150 in the single day.
Also anything voted on between 00:00 and 03:00 UTC that gets deleted by the Roomba refunds the votes placed against them one they're deleted so it's not unusual for someone to be able to vote a lot more than 40 times per day.