Fix the behavior of TTL

The 30 day TTL limit before interpreting TTL as a UNIX timestamp is incredibly unintuitive
and prone to create bugs. Instead, only interpret this value as a UNIX timestamp when it's
remotely in the range of being a valid UNIX timestamp. I chose the timestamp of the date this
project was started. This is a backwards compatible change for those who use timestamps as
TTL and allows for TTLs greater than 30 days (in fact, up to ~32 years)