SlackBuildsOrg/system/tzupdate

tzupdate

tzupdate is a fully automated utility to set the system time using
geolocation.

Internally, this geolocates you, gets the timezone for that geolocation,
and then updates the system's local time zone.

You can see what tzupdate would do without actually doing it by passing
-p, and specify an alternative IP address by using -i. This is not an
exhaustive list of options, see tzupdate --help for that.

NOTE: Do not trust its results blindly. It does what it can, but
determining a time zone based on an IP is inherently unreliable.