Web pages with clocks display UTC instead of local time

Running Screenly OSE on a Pi3B; installed the latest version of Raspbian Lite using Raspberry Pi Imager and used curl to install Screenly OSE’s development/master branch. I need to use the master branch since the stable version’s browser is unable to visit Solar Edge links.

Visiting our Solar Edge page (SolarEdge) or using a quick JS time check from w3schools (W3Schools Tryit Editor) pulls UTC.

timedatectl returns this:

pi@raspberrypi:~ $ timedatectl
Local time: Tue 2021-04-20 15:42:53 CDT
Universal time: Tue 2021-04-20 20:42:53 UTC
RTC time: n/a
Time zone: America/Chicago (CDT, -0500)
System clock synchronized: yes
NTP service: active
RTC in local TZ: no

Running docker exec -it screenly_srly-ose-viewer_1 date also returns my time zone. I went back and tried the stable version again just to see if it was having the same issue (using the w3schools link, since the Solar Edge wouldn’t load), and it was displaying my timezone. Not sure what else to try here and all of my searches for similar issues returned threads stating this issue was resolved a few sprints ago.