Interesting thought, similar to some I’ve had on relation to my use of Notion. We of course need the addition of @date type functionality in the first place. And since we can’t @mention in titles, that would be a whole feature in itself as well, and one that might be useful but also seems potentially problematic to implement well and/or prevent weird things happening with.
I wouldn’t want any date-like text to be automatically picked up in this way, I think it should only be dates explicitly “tagged” or "mentioned. So I’d suggest that perhaps any time you wanted to include a date in a title it should be an auto-generated (formula) title, although I’d personally like that to be done on a per-entity basis and not Type-wide.
Going back to the original idea itself, I don’t really see it being ideal to integrate the dates view into the activity stream. What I wanted from Notion also seems applicable here: a date “feed” one could connect to from any View, e.g. create a Calendar View and you can select “Tagged dates” as the source of dates, perhaps even letting you filter by App or Type. Then all the tagged dates @11/15/2020, etc. would show up on the calendar. Or you could switch to Table view and see them that way, with one column being the page they are on, maybe another being the day it was tagged with that date. Just thinking out loud a bit here. But the point was I thought essentially that tagged dates anywhere in the system should go into a central feed that was available to display or use like any database data source would be.
Does that sound like it would address the needs you have in mind as well? Or is there some particular reason you’d want it integrated into the activity feed, and if so, what would that actually look and work like? For instance I didn’t envision the activity stream having any kind of date selector, I figured it would be like most of them are, a sequential list of notifications/activities, with hopefully a read/unread status indicator (and a way to dismiss individual or global notifications). This would of course include date reminders that had been triggered, but the “data feed” + calendar view seems more like a comprehensive way to interact with and manage tagged dates.