What TTL should a DNS record have? 5 minutes, 1 hour or 1 day

A TTL only affects the next fetch. When you change a record, resolvers that already cached it keep the old answer until their copy expires, so the old TTL sets how long the switch takes. Lower the TTL to 300 a day before a server move (longer, if the current TTL is more than a day), make the change, check it, then put the TTL back.

Very short TTLs have a price. Every expired copy means another round trip to your name servers, which adds delay for visitors on a cold cache and more load on your DNS host. A TTL of a few seconds turns almost every visit into a fresh lookup.

Some starting points:

• 300 seconds (5 minutes) for records behind a failover setup or anything you expect to move soon.
• 3600 seconds (1 hour) for websites, mail and most other records.
• 86400 seconds (1 day) for NS records and names that almost never change.

The DNS Lookup shows the TTL in plain time and in seconds. It's the time left on the resolver's copy, which is why two resolvers rarely show the same number.