I assume you are on the OpenWrt 19.x based version of the firmware? I just tried on my OpenWrt 22.x, and your example and also 100 years later works fine: date --set '2150-01-01 20:00:00' Thu Jan 1 20:00:00 CET 2150 I know that musl (the libc replacement OpenWrt uses) has switched to 64bit time_t sometime between 19.x and 22.x as I had to fix some tools that were not prepared for 64bit time when I switched to 22.x So if you upgrade to 22.x or later sometime in the next 14 years, you'll be fine