Thank you guys for your help! Though my extract_datetime field has %Y-%m-%d %H:%M:%S but when i executed the below search, came to know it is only extracting %Y-%m-%d .
sourcetype="something" extract_datetime= * | table extract_datetime
Hence updated my search string as below and it works perfectly. Thanks again 🙂
sourcetype="something" extract_datetime= *
| WHERE strptime(extract_datetime,"%Y-%m-%d") >= relative_time(now(),"@d")
