There's BC, AD, and if you're an England opening batter, AS.
Since Andrew Strauss retired at the end of the 2012 English summer, 12 full-time openers tried to fill the void opposite Alastair Cook. A further six were then used to mitigate the loss of Cook, too, bringing us to 18 souls with the unenviable task of replacing two who stepped away from the game with their legacies and legends cast in stone.
So - have the 18 been rubbish? Well, no. They were far from chancers. Opening the batting is hard, particularly in England, where the guys at the top have averaged 30.78 AS - lower than everywhere bar West Indies (minimum two Tests). It's hard. Really hard. As Test coach Brendon McCullum joked during the summer: "The last two guys who nailed it at the top of the order are both called 'Sir' in this country."
Still, though - 18 openers, in 10 years After Strauss? 18, England? That's insane, and evidently unworkable. The longevity and stickability of many of them meant they would eventually come again on weight of County Championship runs. The same names, vaguely the same results, broadly the same criticisms and very often the same demoralising experiences - whether dropped unceremoniously, dumped from the team WhatsApp group, hearing second-hand of team-mates lamenting their output or, as has happened in the past, shlepping to retrieve their kit from the dressing room of the venue of their final cap while the rest of the squads' bags were transported to the next ground.
But they were failing in the same system, under the same expectations of those spoiled by their knighted predecessors and with the same guidance of "go and do some opening or we'll find someone else who will". So when Zak Crawley and Ben Duckett combined for 232 on day one in Rawalpindi, slotting in at No. 8 in England's all-time list of highest opening stands against any opponent, a century each by their names, and setting the perfect platform for England to get to stumps on 506 for 4, it was hard not to reflect how this new regime might have changed the English opener experience for the better.
It is most obvious in the case of Crawley. Because in many ways, his 122 won't change the conversation around him. Backed throughout the summer by McCullum, his captain Ben Stokes and Rob Key, a confidant of Crawley long before he became director of England men's cricket, he became something of a lightning rod for accusations of nepotism. A summer average of 23 from 13 innings was helped by an unbeaten 69 in the final Test of the season against South Africa. It was 17.25 prior to those runs and that red ink.
The outward talk was of a high ceiling: that when Crawley gets it right he can be one of the more destructive openers on the circuit. And yes, it's hard to discern which was flattest: the pitch at the Pindi stadium, Pakistan's bowling attack or their fielding. But from striking 14 off the first over - the most England have taken from the opening over of a Test - to being unbeaten on 91 at lunch, then getting to three figures for the third time, from just 86 balls, there was an element of vindication here. Not just of Crawley but the work put into him behind the scenes.
Stokes and McCullum have done well to wean the 24-year-old off technique and more on feel, especially given he is an insatiable netter. Positive reinforcement has been consistent but not laid on too thick to devalue their words. Both spent large parts of the summer creating comfortable spaces for Crawley. Such as when Stokes and McCullum manufactured a three-ball group so they could accompany him for a round of golf. Once that was complete, they sat around with a few beers and Crawley opened up about his worries, leaving them contained in that time, at that clubhouse.
Their treatment of Crawley has polarised, especially among batters who opened before and those who think their time should have come. The idea the England squad is a closed shop is building in the domestic scene, but much of that seems rooted in the fact Crawley's treatment is a luxury never seen before. It is, ultimately, a good thing.
"I feel like it was just we weren't playing great games of cricket," Crawley said of the time before McCullum, in which he also struggled with just two centuries in 21 caps. "We weren't getting the most out of our talents playing the way we were and playing it safe and Baz always backed us to play positively.
"It was not easy opening the batting in the summer. I thought I played okay at times and played some decent knocks but I did not get the decent score."
Another change of tack from the management has been to focus more on the "partnership" side of opening.
Ahead of this tour, the decision was made to drop Alex Lees. A summer's worth of play had seen him average 25.15, higher than Crawley. At times they dovetailed well, with two century and two half-century stands between them in 19 innings. Their collective 536 was the second-best combination of openers since Strauss' retirement that did not feature Cook. Coincidentally, the pair in top spot - Rory Burns and Dom Sibley - are two who shared unflattering traits with Lees.
It was felt Lees, like Burns and Sibley, had trouble turning over the strike, and as such seemed to put undue pressure on the batter at the other end. Harsh, no doubt, especially given Burns and Sibley were the only openers not named "Cook", to have played since the end of the 2012 summer and scored 1000 or more before Crawley joined them with this knock. And while that analysis reads a bit like making Crawley feel a little more comfortable, in Duckett there is an element of symbiosis.
They hit the similar lines and lengths to different areas: Crawley favouring drives on the up and short-arm pulls, while Duckett focuses square, particularly against the Pakistan seamers when he would regularly square drive wide deliveries behind point. The left-right combination is one thing, but if would mean nothing if they weren't getting the other on strike, with regular tucks to favoured areas - Crawley into the covers, Duckett around the corners.
By lunch - 174 for 0, the most by England in the opening session of a Test - the hosts' attack was shot of confidence, with both notching half-centuries at a run-a-ball or better. Another first for English openers, by the way. It took until the 39th over for Pakistan to register their first maiden of the innings. By then, both Duckett and Crawley had been back in the dressing room for 15 minutes.
"I'm pretty small and 'Creepy' is pretty tall so I think where they bowl is very different to both of us," said Duckett on how he and Crawley complement each other. "The areas we hit are very different as well. Bowlers have to come round the wicket to me and change the line. It is pretty fresh but it is a good start and we are really happy."
At a time when the general ethos around the Test side is riddled with white ball-isms, from the selfless play preached to the presence of Liam Livingstone in this XI, Duckett might be the first rough diamond to need little polishing.
Under previous regimes, notably on a chastening 2016-17 winter in Bangladesh and India for Duckett, his manner was derided. The aerial options and the regulation- and reverse-sweeps saw him unfairly regarded as a player who would eventually be found out. The attacking options he would resort to when under pressure chastised as the futile slapping of the waves by a drowning man.
Thankfully, those barbs, a broken hand and years of losing his authentic grip did not rob him of his natural instincts. There was plenty of crossover between 1012 runs at 72.28 in the Championship for Nottinghamshire and 223 at a strike rate of 159.58 in the seven-match T20I series in Pakistan earlier this year.
The latter proved useful for his maiden hundred, from 105 deliveries: "I think especially facing Naseem [Shah] and Haris [Rauf] and performing against them in the T20 series it gave me confidence coming into this series, albeit in a different format, because I knew what the pitches were going to be like." It is a milestone that could be the start of a fruitful emergence as an all-format player at the highest level.
Just to reinforce the bond with Crawley, he convinced his taller partner to review a dismissal that otherwise would have cost him three figures. On 99, Crawley was subject to an lbw appeal off Naseem that was given out on the field.
"I thought I was out," revealed Crawley in his press conference while sat next to Duckett. "But 'Ducky' knew it was missing and has a good eye. I felt I had missed an opportunity so it was an unbelievable feeling and made the hundred more special."
Duckett interjected: "It looked like it was missing. I think if it was hitting middle halfway up I would have told him to review it anyway."
While the pair were going back and forth fielding questions on their work, two other centurions, Ollie Pope and Harry Brook, were on the outfield singing both their praises.
"It started from the get-go, really," mused Pope when asked to cast an eye over 75 overs of destruction. "Fourteen off the first over?" Yep, 14. "It just put them under pressure straight away. It looked like there wasn't really anywhere they could bowl to those two the way they were going. It was the perfect way for those boys to set us up and start the series in that fashion."
Having set such high standards, the only way is down for England's newest dynamic opening pair. What is for certain is their stand of 233 will now be regarded as a marker to beat rather than a limit. We are just one Test into the winter, and in conditions where opening batters tend to do well. But already Crawley and Duckett have the feel of a reliable partnership to facilitate more of the chaos England inflicted on Pakistan onto the rest of the world.