Expire time and TTL is slightly different topics in hostmaster's world.
You asked about TTL. TTL (TimeToLive) define (as name states), how long properly configured 3-party DNS-server will store received information in own cache, answer to clients with this data and will not forward request to external world.
TTL linked with every RR in zone and stored in file (or other source) with zone definition.
Default TTL defined in SOA RR and apply to all data without RR-specific TTL inside zone
Your this question poorly related with "domain-transferring" tag