...The Night of the Watch must be after that, but we don't know exactly how long after...
Yes, we don't know exactly when Adrian arrives. Page 6 seems to be only a day or two after his arrival though, and that day must be fairly close to Christmas because Laura is about to start a "relationship" with Derek that she later describes to Vic as a holiday fling. And she's seeing Zenon because of her concerns about "the new term". Also, judging by Caitlyn's breast size, she has already been on the Mantis squad for a while. So I'm inclined to think Adrian's arrival is not too long before Christmas. Things are easier to pin down once the story does get to Christmas.
A "Quine Organization" calendar is shown in 79 that happens to tally with the days in January 2012. (That page was published in 2012.)
The calendar places the Night of the Watch on Monday 2 January ("Le clinique. Merci, Adrian!")
It also places "Laura, dinner" on Thursday 12 January. Funnily enough, we're looking at the calendar while Laura is starting to invite Raven to the SJI for that dinner, although of course in the end Laura doesn't attend and Raven is left having to make do with Erin.
Page 137 occurs while Erin and Raven are at it, and Daphne said in the forum thread for g7:
"Although this isn't something I want to burn into stone quite yet, episode 137 can be assumed to take place on January 12, 2012."
The narrative has given us a clear and unbroken succession of days since then, such that we
should now be at the beginning of Sunday 22 January 2012. But that would place 754 on Saturday morning, and in that page Hitomi asks Amaltheia if she's doing anything on Saturday.
So I think we have to assume that we're actually supposed to be a few days on from there - somewhere in the week leading up to Dani and Jacqui dancing at Sawyer's, which is marked on the calendar for Saturday 28 January.
(For what it's worth, it's just about feasible that Dani was Zenon's last patient before the start of his one-week vacation. I think the intention had been for Raven's invitation to be given straight after the Night of the Watch, placing her date with Erin a whole week earlier. But someone remembered Zenon's holiday and realised they needed to insert some time to allow for that. I suspect that's
why we're shown the calendar in 79: it lets us know that we've missed approximately a week of the action.)