Hi @suryakant30 

1. gs.nowDate() and gs.nowDateTime() are not available in Scoped Applications

Ensure you are using  GlideDateTime class instead

2. If you are not using scoped app , then it could be the case

Your approval_date is Date/Time field  where you are trying to store gs.nowDate() which  returns a date string

Ensure , in that case  - you are using gs.nowDateTime() for Date/Time fields.