I registered as a delegate 16 days ago but tzstats still says I haven’t registered as a delegate. In the case of tzstats, the delegation operation shows up in the delegation tab. How long does it take after registering to show up in block explorers?
For registering a delegate to bake, block explorers should show success as soon as the operation is made on the blockchain. Unless there is a fork, this will stay true unless you are inactive. This means as long as you have enough rolls, you will be given rights after 7 or 8 cycles (depending on snapshots).
As far as obtaining actual rights, regardless of implementation of the block explorers, the Tezos blockchain decides baking/endorsing rights for cycle
N in cycle
N - 5. So for baking rights in cycle
100, the rights are finalized in cycle
95. To be specific, with our example, by cycle
95, the blockchain has chosen the exact snapshot from cycle
93 to use for rights (1 chosen from 16 possible snapshots). Snapshot affects how many rolls you are counted for rights and/of if your delegation registration makes it in cycle
Obviously different block explorers will show things at different times based on their unique implementations. But understanding how it fundamentally works for the blockchain can help set decently good expectations for block explorers.