Look at the rescheduled 1872 Cup clash between Glasgow and Edinburgh in the RaboDirect PRO12 this coming Saturday: change the date and you change just about every meaningful dynamic about the match, from how it is likely to be played to the significance of the result.
Had the game gone ahead as scheduled at New Year, it would have been virtually a Scotland trial ahead of the RBS Six Nations Championship.
It would have been played in appalling conditions with a limited crowd and mud, wind and rain making constructive rugby impossible.
Though most of the players would have been vaguely aware the result would have an effect on end-of-season placings, most would have been concentrating on more immediate rewards, including the chance of Scotland caps.
As we all know the match was rained off; so roll forward to next weekend when the game will finally be played.
The Six Nations is gone, so the trial element has disappeared; conditions should be close to perfect, so neither side has an excuse for not entertaining the crowd.
The stands are in place at Scotstoun for the IRB World Series Sevens so capacity has been trebled to around 15,000 and Glasgow are talking about a record attendance.
And, finally, it is now a match where both sides know Glasgow's season is at stake. After Friday night's 27-9 win over Ulster, Glasgow's play-off fate is in their own hands.
They are close to being secure in the top four, but to ensure a home semi-final they need to keep winning and probably need to start picking up the scoring bonus points that have been eluding them most of the season.
Edinburgh, meanwhile, have no serious hopes of achieving anything apart from maybe a morale boost before the summer.
Glasgow's win over Ulster, one of their play-off rivals, was an impressive performance that cemented their status as having the best defence in the league. However, for the second week in succession, they did enough to claim the extra point but had to settle for three tries and the win alone.
Perhaps that was fair. Centre Mark Bennett, who was awarded the final score, admitted he did not think he had grounded the ball. At the other end Nick Williams, the Ulster No 8, was adamant he had got the ball to deck but the pile of bodies around meant there was no television angle that showed it.
A veteran of the derby games against Edinburgh, scrum-half Chris Cusiter knows what they are all about and says the shift from winter to spring has probably helped Warriors' cause.
"On one hand having two games postponed means we are playing week after week until the end of the season," he said. "On the other hand we have a firmer pitch and better conditions and I always prefer that - I guess everybody does - so it should be a better game.
"At the moment we have the momentum, so I hope it has come at a good time for us. You are used to those back-to-back fixtures over the festive period, so playing it in April is different."
The extra four months that have passed have increased the foreign influence at Edinburgh, with more players having been signed and more of those brought in during the first half of the season getting regular places.
That also changes the dynamic of the match. "I used to enjoy playing against Mike Blair. I don't know if Greig Laidlaw will be playing but I don't think he will," Cusiter said. "It adds an edge when you know the guys personally but the teams tend to cancel each other out a bit because we all know each other's strengths and weaknesses.
"Most of the Scottish guys here keep an eye on what is happening at Edinburgh. There are a lot of changes and they are going in a certain direction and are definitely in a period of transition.
"When we played them through there they were tough to beat, really physical. In the past we have had a physical edge but it certainly did not feel like that in the match just after Christmas. They are capable of beating anyone, but a bit inconsistent which, with a new coaching team and players, is bound to happen.
"They have potential with a lot of good players. If they put it all together they are definitely capable of winning but they have had some strange results — I don't know if they are finding their feet a bit with the new systems and all that.
"This is my last chance to achieve anything [Cusiter moves to Sale in the summer], so I hope we can keep building to the end of the season.
"It will be really, really tough to leave - Glasgow is brilliant. I am excited about the future, but I have had a great time here."