Have a look at the cat API : you can get the list of available parameters via http://localhost:9200/_cat/indices?help
To get the creation date of your indexes, you would use creation.date (or creation.date.string). For example, use
http://localhost:9200/_cat/indices?h=h,s,i,id,p,r,dc,dd,ss,creation.date.string
For full header names:
http://localhost:9200/_cat/indices?h=health,status,index,id,pri,rep,docs.count,docs.deleted,store.size,creation.date.string&v=