Currently, the time crate has support for years ±100,000 inclusive (negative years are astronomical year numbering). I am currently in the process of redesigning and optimizing a number of things for a 0.3 release. Some things could be simplified or further optimized were the range of valid years restricted.
On the main branch, the range is currently widened to ±999,999 inclusive, but I am obviously looking to narrow this. +1 to +9999 is the absolute minimum range I'm even considering, but ±9999 is what I'm eyeing. What range of years would you like to see support for?