It's a shame that creating DateTime objects with microsecond resolution is as hard as it is, so it probably is worth noting this at the point where you'd generally want to use them. Good job!

Some feedback on the patch itself (none of this is bad; more just a reflection of our norms for the manual — coding style, if you will):

- It's rare that we directly reference bug reports in the manual (in fact, there's only one reference page that does so at present, and that one's probably wrong). I don't mind noting that it's harder than it should be to create a DateTime with microseconds and describing how to do so, but we probably don't need a link to the bug report as such.

- If the reference does stay in, the usual format would be to link using an entity for the base: this would be something like
<link xlink:href="&url.php.bugs;49779">#49779</link>. In general, we never place direct URLs in the manual, as this makes it harder for translators: genuinely new URLs (which this isn't, of course, as we have url.php.bugs already) go into doc-base/entities/global.ent and are then referenced from the reference page(s) that need them.

- Class names should be surrounded by <classname>, so <classname>DateTime</classname> — this is for both formatting and linking reasons.

This bug has been fixed in the documentation's XML sources. Since the
online and downloadable versions of the documentation need some time
to get updated, we would like to ask you to be a bit patient.

Thank you for the report, and for helping us make our documentation better.