[Recently](https://meta.stackexchange.com/q/55037/168244), the network implemented a date range specification as part of the "Ninja Search Options". From the linked post, here's [an extract on the implementation](https://meta.stackexchange.com/a/162064/168244):

> This is now implemented, here are some examples:
> 
>  - `created:2012` (created between 2012-01-01 and 2012-12-31)
>  - `created:2012-04` (created between 2012-04-01 and 2012-04-30)
>  - `created:2012-04-05` (created on 2012-04-05, 24 hr UTC range)
> 
> The above date formats can be applied to a range as well with `..`,
> like this:
> 
>  - `created:2012..2012` (created between 2012-01-01 and 2012-12-31)
>  - `created:2012-03..2012-04` (created between 2012-03-01 and 2012-04-30)
>  - `created:2012-01-05..2012-01-10` (you get the idea)
> 
> Those are for when a question is created.  For the last time it was
> active (same as the active tab) you can use `lastactive:` the same way
> as `created:` above.

So, you could find the specific question you remember seeing last and visit it using the link:

    https://tex.stackexchange.com/q/<number>

Then, identify the date of that question and perform a search based on that creation date. This will list posts in newest-to-oldest form (technically not what you're after). Here's how to [search for *questions* tagged **amsmath** between Jan 2, 2013 and Mar 1, 2013](https://tex.stackexchange.com/search?q=created%3A2013-01-02..2013-03-01+is%3Aquestion+%5Bamsmath%5D):

    is:question [amsmath] created:2013-01-02..2013-03-01