Ivy Day is March 27 this year. It sounds like March 26 is a reasonable guess for Vandy.
It looks like last year Vandy sent out an email the day before decision release, around 4:15 central time, announcing a 5:30 pm CT decision release the following day. First post of actual decision release ended up being at 5:11 pm CT though it looks like it took a few minutes for others to be able to get into their portals.