This was the day when Celtic's Championship hopes went up in smoke and they can have no complaints as Hearts outplayed them and thoroughly deserved the win.
It was Hearts boss Craig Levein's first victory over either Old Firm side in 21 attempts and it came in dramatic fashion.
Hearts came from behind after Henrik Larsson notched his 39th goal of the season and the winner came with literally the last kick of the match.
The goal hero came in the unlikely form of Austin McCann who hammered home a 35-yarder for his first Hearts goal in three seasons.
Hearts had matched Celtic all over the pitch and although home keeper Tepi Moilanen had to make a couple of fine first-half saves from Alan Thompson the home side had their chances as well.
Mark De Vries sent a couple of efforts on the turn narrowly over the bar and only a fine block from Johan Mjallby denied young Graham Weir.
After the break a fine burst from Andrew Webster set up Phil Stamp and Rab Douglas had to race off his line to save with his legs before palming an Alan Maybury volley over the bar.
Douglas' saves could have been decisive as Didier Agathe raced past McCann and provided a perfect cut back for Larsson to nudge the ball home from close range.
You would have put your shirt on Celtic going on to win but Hearts had other ideas as they rolled their sleeves up and set about the task in hand.
There was a touch of good fortune about the equaliser when Scott Severin's mis-hit shot was deflected under Douglas' arms by Stamp.
But Celtic got the breaks when Jean Louis Valois volleyed against the crossbar and then Mjallby popped up on the line to save a net bound header from De Vries.
And as Celtic threw caution to the wind in search of the winner they desperately needed they were hit by Hearts' last second goal.
Severin broke out of defence and it looked as though he had delayed too long as Celtic retreated in numbers.
But his sideways pass was met first time by McCann and his glorious effort screamed past a startled Douglas and in off the post to hand Hearts a dramatic victory and leave Celtic in despair.