Can we convert a non-TTL index into a TTL index?

I have a existing index which is a non-TTL index.
First question is Can I create a index with same field (means Can I create index with ‘date’ field?)
If the answer is yes please do explain how?
If answer is no then how can we convert this non-TTL index into TTL index (add timeToExpire in options)

      "key": {
        "date": 1
      "options": {
        "name": "date_info",
        "background": true,
        "sparse": true

Hi @Vartika_Malguri have you tried running something like the following (taken from the TTL Index documentation):

  "collMod": <collName>,
  "index": {
    "keyPattern": <keyPattern>,
    "expireAfterSeconds": <number>

This will go through and update an existing index with the expireAfterSeconds field. I just tested this out on a normal index and the document was deleted after the expireAfterSeconds period passed.

Yes… I have tried this …This didn’t worked for me
It says no expireAfterSeconds to update

Can you state what version of MongoDB you’re using? I just tested this out on version 6.0.0 and it worked.

Quick note, I just tested with versions 5.0.10 and 4.4.15 and was able to do the same as I did on 6.0.0 and the process worked on those versions as well.