Change lockscreen time and date font? Starting from Android 6.0, Google altered how their lockscreen looks in AOSP, presumably to increase readability:


Digital clock is smaller
Digital clock uses a bolder font, presumably Roboto Medium
Date text is ALL CAPS
Date text has a noticeable character spacing


A comparison can be seen in the pic below.



It seems that this is Google's design vision going forward, as Android 7.x only kept or reinforced upon those points, and the recently released Fuchsia OS preview is in the same style.

However, as good as Google's intention might be, I'm not a fan of all these points above, and now that I see Google is determined to push it (Fuchsia), I'm determined to revert it back to what it was in Android 5.x. I'm rooted, have a custom recovery, and know how to decompile and recompile APKs, so I should be ready for whatever's needed.

Ideas?
After some more searching, I finally came across an XDA-Developers thread explaining how to do it - or rather, how to do the reverse action of what I want to achieve (credits to the original author there). I'll post an excerpt of the core part and reverse the action yet again to make it fit my purpose.


  
  Install apktool.
  Install your framework-res.apk by executing apktool if /path/to/framework-res.apk.
  Decompile your SystemUI.apk by executing apktool d /path/to/SystemUI.apk
  Go to the decompiled SystemUI folder and open res/values/styles.xml.
  Search for big_thin and replace sans-serif-light behind &lt;item name="android:fontFamily"&gt; with sans-serif-thin.
  Open res/values/dimens.xml.
  Search for widget_label_font_size and replace 14.0sp behind it with 16.0sp.
  Open res/layout/keyguard_status_area.xml.
  In the two lines starting with TextClock and TextView, remove android:textAllCaps="true" and android:letterSpacing="0.15".
  Rebuild SystemUI (preserve its signature) by executing apktool b -c SystemUI.
  Push the finished SystemUI.apk back to where it was using a method of your choice, set correct permissions, then reboot.
  


The end result is pictured below. Font size might still use some tweaks, but generally favorable result.



P.S.1: For the record, and for ROM makers who are interested: you can also modify the same files prior to building the ROM - find the files above in *build-folder*/frameworks/base/packages/Keyguard/.

P.S.2: Interestingly, while searching for "reverting the font on 6.0+ back to what it was in 5.x" didn't return anything, searching for "changing the font on 5.x so it looks like 6.0+" (the opposite) did return more favorable results, as there were quite a number of Marshmallow wannabes back then. I guess that's a lesson learned in Google-fu...