I believe after 2012 both Linux and Windows servers changed how they account for a leap second from having two 59 seconds to adding a 60th second. I understand this change was done to avoid a lot of the crashes that happened to websites last time; where having two things happen at the same second is impermissible. While at my work there were not problems in 2012, because of this change we're a bit worried about it, so we're just closing all transactions for two minutes around the leap second.
I believe after 2012 both Linux and Windows servers changed how they account for a leap second from having two 59 seconds to adding a 60th second. I understand this change was done to avoid a lot of the crashes that happened to websites last time; where having two things happen at the same second is impermissible. While at my work there were not problems in 2012, because of this change we're a bit worried about it, so we're just closing all transactions for two minutes around the leap second.