In a normal Chimera system, your date/time is synchronized with
the chrony daemon, which is installed by default with the full
base package.
If you have a smaller system without it installed and want it, you can install it like this:
# apk add chrony
This will also automatically install the service links to enable it. If you don’t want it enabled by default (for example you are using another solution, or just don’t want any NTP at all and instead only rely on your hardware RTC), mask them:
# apk add '!chrony-dinit-links'
To enable the service after that:
# dinitctl enable chrony