odhcpd reports DHCPv6 lease time in seconds => meaning lease time duration. Which is unfortunately treated as unix timestamp in reForis Lan page (e.g. 1970-01-01 some_time).
DHCPv4 lease time, on the other hand, is reported as timestamp of end of the lease (e.g. 2022-01-11 20:41).
Unify lease time format for both DHCPv4/6 to the "end of the lease" format.
Closes: #258 (closed)