Lyve Lyfe Lyke Jupiter Ascendinge

Between Act I and Act II, the townspeople of Tassing age and change. Some of them begin going gray (or go grayer). Some grow longer beards or hair. Some have cheekbones become more prominent, or have lines on their face that develop or deepen, even subtly. And of course it's especially obvious with the kids of Tassing, who are growing from babies into children, and children into teenagers.

Even those characters who don't have visual changes to their faces or hair have differences to their clothing to show that time has passed. They've changed, even if it's only replacing or restyling old clothes, or growing out their hair. People have died, been born, gotten married, moved into town, built new businesses, taken up new ideas - the growth and change is often modest, but it's visible.

But at Kiersau Abbey...

... nobody changes - so much so that most of the monks and nuns don't even have different portraits between Act I and Act II, despite the passage of seven years.

For those that do, the only change is to the color of their habit (the seven years between Act I and Act II would encompass the entire period between entering the abbey and solemn profession, so anyone who was a novice when Andreas was there in Act I would have necessarily professed by Act II). The only other one who changes is Aedoc, whose "image" becomes more worn - but even he doesn't change facially. (Compare him to the visible aging of Ill Peter, another elderly male character.) None of the members of Kiersau physically change, visually, in those seven years. No lines on their faces, no gray hair, no wrinkles, no beard growth, no drooping, no aging, nothing.

The only ones who change regardless of the outcome of Act I are Cecilia, who was far more worldly and savvy than her counterpart, more proactive and less caught up in Kiersau as a bubble; and Piero, who understood and accepted that change was inevitable and didn't fear it. And the only way that they could change was to die, and disappear altogether.

And for all that there's been at least one major change to Kiersau with the closure of the scriptorium (and possibly more, depending on Ferenc and Matilda's fates in Act I), almost nothing has changed in terms of how Andreas/the player sees and experiences the abbey. Of those characters in the abbey who have "grown up", Zdena is still half-heartedly tending to the remains of the library under Illuminata's supervision (and Illuminata herself, though she's now Mother Superior, is still in the library sorting books). Lukas is still in the kitchen, and still can't quite figure out what to do without Wojslav directing him. Volkbert is still doing the menial, grubby work nobody else wants to do. He even lampshades how taking his vows hasn't really changed anything except the color of his habit:

I'm a monk now. . . . I still do the same work, but now I have the same robes as the other brothers.

One expects the abbey to change more slowly than the town, given that the monks and nuns aren't likely to be getting married or having children (one presumes, at least); but even those characters who have, in name, taken on new roles are still functionally doing mostly the same things they were doing seven years ago.

The only members of Kiersau that we see change, grow, take on visibly different roles, and age are the ones we see in Act III, after the abbey has been destroyed and they've moved on elsewhere.

Obviously Kiersau Abbey is not some kind of actual pocket dimension where time doesn't move (unless . . . ?). But it's posited even within the text of the game as a deliberate anachronism, a medieval holdover in the early modern age; and it's set against the inescapable presence of the Church's inertia versus the looming Reformation, and the growing social unrest against the feudal status quo. A major theme of the game is the inevitability of change and loss, and how being able to accept it and move on is essential for growth/survival. And it's clear that the stagnation has reached such a point that there can be no lasting change on a social scale in Tassing until Kiersau burns.

So all that said, I don't think the visual contrast between the clear progression of time in Tassing, and the lack of it in Kiersau, is a coincidence.