It marks the thing something is done with, or the point at which something becomes settled. Half the lines here use it with this or today to mean as of this moment: the future is now predictable, the previous round is void, the anniversary falls today. The near neighbour is 로서, which marks a role or status rather than a means, and Korean speakers confuse the two constantly; the line about reacting as an INFP is one of those slips, and would be 로서 in careful writing.
Register: somewhat formal; summing-up and announcements