sync date to an RTC without hwclock

[James Hughes]

I have a NARD device out in the wild that lacks internet connectivity and
needs to have the RTC updated. Normally this thing (an art installation) is
connected to wifi, and just uses NTP - but this is a special temporary set
up without wifi.

It appears the base NARD SDK (v1.0, I think) has busybox set up without
hwclock, so I'm wondering if there's another standardized way to sync the
date to the RTC? I'd like to avoid recompiling and shipping out an image
just to add hwclock to busybox. Any ideas?