I'm not sure this is a problem with Start10 or with Win10 1803, but since I use Start10 universally on my Win10 systems I can't really be sure. So I thought I'd ask here first, before going over to TenForums, since I have a feeling it's Start10.
I have many icons on my taskbar, so I have a double-high taskbar. I also normally have "use small icons" checked on the taskbar settings. the notification area is also double-high of course. Desktop resolution is 1920x1080 on the FHD Lenovo screen. Text size is set to "medium 125%", so this issue may be from a Windows DPI problem... don't know.
Normally, the right side of the notification area would have the date and time shown on two lines (for a single-high taskbar) and the day would also show on a middle third line if space permits (for a double-high taskbar). Well, today I happened to notice there was no date/time info where I would expect to see it. This is a brand new Win10 from-scratch install (on a Lenovo Thinkpad W530 laptop) which started from 1511 install media and went to 1803 through the normal Windows Update.
So I began to experiment. Turns out if I turn off "use small icons" the date/day/time appears with in white font against the dark background of the double-high taskbar:

But if I turn on "use small icons" the taskbar quickly resizes to be a bit smaller, and the date/day/time is re-painted briefly to have a bit less room between the three lines and the white text font is visible briefly. But then all the characters disappear.

I can make the white characters reappear simply by going back to large icons on the taskbar. And again if I go to small icons, the taskbar and notification area re-size with the white characters still briefly visible before they once again disappear.
So this may be a Windows graphics/DPI issue due to the 125% text size perhaps, where it is Windows that is wiping out the characters because it thinks there's not enough room to properly display it.
Or, it may be a Start10 issue dealing with characters and 125% text and the slightly reduced taskbar size with "use small icons".
Or, it may be a Win10 1803 issue. Don't know because all my Win10 machines are at 1803 and they all exhibit this symptom.
Just for the sake of experimenting, I tried going to a single-high taskbar. In this configuration there is no "day" shown on a middle third line. Instead Windows only presents date and time. Again, with "large icons" the two remaining date/time text lines appear.

But if I go to "small icons", the very same symptom results where the taskbar resizes quickly while the date/time white text is shifted slightly but remains visible briefly... and then the text disappears.

Again, going back to "large icons" resizes the taskbar a bit and brings back the white two-line date/time text.
In summary, the issue could be from Win10 and 125% text size. Or it could be related to this but due to 1803. Or it could be caused by an issue with Start10 along with 125% text size and/or 1803.
nVidia K1000m graphics with latest retail 392.00 driver.
Anybody?